Prospectus by Investment Company (Form 497)

BRIDGE BUILDER TRUST

Bridge Builder International Equity Fund (the "International Equity Fund")

Supplement dated September 25, 2025

to the Statement of Additional Information ("SAI") dated October 28, 2024, as supplemented

This supplement provides new and additional information beyond that contained in the SAI and should be read in conjunction with the SAI.

The Trustees of the Bridge Builder Trust (the "Trust") have approved an amendment to the investment sub-advisoryagreement among Olive Street Investment Advisers, LLC (the "Adviser"), Massachusetts Financial Services Company (d/b/a MFS Investment Management) ("MFS"), and the Trust, pursuant to which MFS now serves as a sub-adviserto an allocated portion of the International Equity Fund.

Accordingly, the SAI is hereby supplemented and revised as follows:

Massachusetts Financial Services Company (d/b/a MFS Investment Management) ("MFS"), 111 Huntington Avenue, Boston, Massachusetts, 02199, is the Sub-adviserfor an allocated portion of the International Equity Fund pursuant to a Sub-advisoryAgreement with the Adviser. MFS is a majority-owned subsidiary of Sun Life of Canada (U.S.) Financial Services Holdings, Inc., which in turn is an indirect majority-owned subsidiary of Sun Life Financial Inc., a diversified financial services company. For its services as a Sub-adviser,MFS is entitled to receive a fee from the International Equity Fund.

Other Accounts Managed by Portfolio Managers and Ownership of Fund Shares.The table below identifies, for each portfolio manager of the Fund, the number of accounts managed (excluding the Fund) and the total assets in such accounts, within each of the following categories: registered investment companies, other pooled investment vehicles, and other accounts. To the extent that any of these accounts are subject to a performance-based advisory fee, this information is reflected below. Information is shown as of June 30, 2025. Asset amounts are approximate and have been rounded.

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As of June 30, 2025, the above-listed portfolio managers did not beneficially own any shares of the Fund.

Material Conflicts. MFS seeks to identify potential conflicts of interest resulting from a portfolio manager's management of both the Fund and other accounts, and has adopted policies and procedures reasonably designed to address such potential conflicts. There is no guarantee that MFS will be successful in identifying or mitigating conflicts of interest.

The management of multiple funds and accounts (including accounts in which MFS, an affiliate, an employee, an officer, or a director has an interest) gives rise to conflicts of interest if the funds and accounts have different objectives and strategies, benchmarks, time horizons, and fees, as a portfolio manager must allocate his or her time and investment ideas across multiple funds and accounts. In certain instances, there are securities which are suitable for the Fund's portfolio as well as for one or more other accounts advised by MFS or its subsidiaries (including accounts in which MFS, an affiliate, an employee, an officer, or a director has an interest). MFS' trade allocation policies could have a detrimental effect on the Fund if the Fund's orders do not get fully executed or are delayed in getting executed due to being aggregated with those of other accounts advised by MFS or its subsidiaries. A portfolio manager may execute transactions for another fund or account that may adversely affect the value of the Fund's investments. Investments selected for funds or accounts other than the Fund may outperform investments selected for the Fund.

When two or more accounts are simultaneously engaged in the purchase or sale of the same security, the securities are allocated among clients in a manner believed by MFS to be fair and equitable to each over time. Allocations may be based on many factors and may not always be pro rata based on assets managed. The allocation methodology could have a detrimental effect on the price or availability of a security with respect to the Fund.

MFS and/or a portfolio manager may have a financial incentive to allocate favorable or limited opportunity investments or structure the timing of investments to favor accounts other than the Fund; for instance, those that pay a higher advisory fee and/or have a performance adjustment, those that include an investment by the portfolio manager, and/or those in which MFS, its affiliates, its employees, its officers, and/or its directors own or have an interest.

To the extent permitted by applicable law, certain accounts may invest their assets in other accounts advised by MFS or its affiliates, including accounts that are advised by one or more of the same portfolio manager(s), which could result in conflicts of interest relating to asset allocation, timing of purchases and redemptions, and increased profitability for MFS, its affiliates, and/or its personnel, including portfolio managers.

Compensation. MFS' philosophy is to align portfolio manager compensation with the goal to provide shareholders with long-term value through a collaborative investment process. Therefore, MFS uses long-term investment performance as well as contribution to the overall investment process and collaborative culture as key factors in determining portfolio manager compensation. In addition, MFS seeks to maintain total compensation programs that are competitive in the asset management industry in each geographic market where it has employees. MFS uses competitive compensation data to ensure that compensation practices are aligned with its goals of attracting, retaining, and motivating the highest-quality professionals.

MFS reviews portfolio manager compensation annually. In determining portfolio manager compensation, MFS uses quantitative means and qualitative means to help ensure a durable investment

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process. As of December 31, 2024, portfolio manager total cash compensation is a combination of base salary and performance bonus:

Base Salary- Base salary generally represents a smaller percentage of portfolio manager total cash compensation than performance bonus.

Performance Bonus- Generally, the performance bonus represents more than a majority of portfolio manager total cash compensation.

The performance bonus is based on a combination of quantitative and qualitative factors, generally with more weight given to the former and less weight given to the latter.

The quantitative portion is primarily based on the pre-taxperformance of accounts managed by the portfolio manager over a range of fixed-length time periods, intended to provide the ability to assess performance over time periods consistent with a full market cycle and a strategy's investment horizon. The fixed-length time periods include the portfolio manager's full tenure on each fund and, when available, 10-, 5-,and 3-yearperiods. For portfolio managers who have served for less than three years, shorter-term periods, including the one-yearperiod, will also be considered, as will performance in previous roles, if any, held at the firm. Emphasis is generally placed on longer performance periods when multiple performance periods are available. Performance is evaluated across the full set of strategies and portfolios managed by a given portfolio manager, relative to appropriate peer group universes and/or representative indices ("benchmarks").

The MSCI All Country World (ex-US)Growth Index (net div) is the benchmark used to measure the performance of Mr. Dwan and Mr. Barrett for the portion of the International Equity Fund allocated to MFS.

Benchmarks may include versions and components of indices, custom indices, and linked indices that combine performance of different indices for different portions of the time period, where appropriate. The qualitative portion is based on the results of an annual internal peer review process (where portfolio managers are evaluated by other portfolio managers, analysts, and traders) and management's assessment of overall portfolio manager contributions to the MFS investment process and the client experience (distinct from fund and other account performance).

The performance bonus may be in the form of cash and/or a deferred cash award, at the discretion of management. A deferred cash award is issued for a cash value and becomes payable over a three-year vesting period if the portfolio manager remains in the continuous employ of MFS or its affiliates. During the vesting period, the value of the unfunded deferred cash award will fluctuate as though the portfolio manager had invested the cash value of the award in an MFS fund(s) selected by the portfolio manager. A selected fund may, but is not required to, be a fund that is managed by the portfolio manager.

MFS Equity Plan- Portfolio managers also typically benefit from the opportunity to participate in the MFS Equity Plan. Equity interests are awarded by management, on a discretionary basis, taking into account tenure at MFS, contribution to the investment process, and other factors.

Finally, portfolio managers also participate in benefit plans (including a defined contribution plan and health and other insurance plans) and programs available generally to other employees of MFS. The percentage such benefits represent of any portfolio manager's compensation depends upon the length of the individual's tenure at MFS and salary level, as well as other factors.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

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