This paper investigates the trade and economy-wide effects of the East African Community’s (EAC) 2022 enlargement, which formally admitted the Democratic Republic of Congo (DRC) and South Sudan. Using a multi-region computable general equilibrium model calibrated to the latest Social Accounting Matrices (2021–2023) and disaggregated by 28 tradable sectors and four primary factors, we quantify the short- to medium-run impacts on GDP, welfare, trade flows, fiscal revenues, and poverty.

Scenario results indicate that full implementation of the EAC customs union and common market rules would raise intra-EAC merchandise trade by 8.4% (≈ US$1.0 billion) within five years, with Kenya, Uganda, and Tanzania capturing the largest shares of new exports. The DRC experiences the sharpest relative gains: real GDP is 2.1% higher and household real incomes rise 1.6% on average, driven by improved market access for copper-cobalt value chains and reduced non-tariff barriers (NTBs) that lower trade costs by 6–9%. South Sudan’s welfare improves modestly (+0.7%), mainly via cheaper imports and investment-goods inflows; however, fiscal revenues contract by 3.2% due to tariff elimination and limited domestic tax capacity.

Community-wide, the enlargement raises aggregate real GDP by 0.4% and lifts an estimated 1.8 million people out of extreme poverty, two-thirds of whom reside in the DRC. Sensitivity analysis shows that gains double when NTBs are halved and triple when accompanied by trade-facilitation improvements.

Conversely, delays in harmonising standards or persistent conflict in eastern DRC erode up to 60% of the projected benefits. The findings underscore the importance of complementary reforms especially infrastructure upgrades, customs modernisation, and peace-building—to ensure that enlargement translates into inclusive and resilient growth.