When last revising the International Standard for Assurance Engagements (ISAE) 3000, the International Auditing and Assurance Standards Board (IAASB) determined that it is in the “public interest” for all competent practitioners (including nonaccounting practitioners) to use the ISAEs. The IAASB imposed conditions on such use, that an engagement’s underpinning ethics and quality control frameworks should be disclosed in the assurance report. Although this explicit determination may encourage wider use of ISAEs by nonaccounting practitioners, the conditions imposed may also act as a deterrent. Using a pre-post design on 2,282 international assurance engagements undertaken by nonaccounting practitioners, we identify increased use of ISAEs and greater disclosure of underpinning ethics and quality control frameworks, although some breaches remain. We further find that switches to ISAEs by nonaccounting practitioners have resulted in enhanced transparency of assurance procedures and independence in the assurance report and an increased share of the assurance services market.