This chapter explores the multifaceted role played by Irish-American leaders in advancing peace and economic development in Northern Ireland. Sparked by the Troubles in the late 1960s, Irish-American engagement initially took divergent forms—from the Irish Northern Aid Committee’s controversial support for the IRA to the founding of the American Ireland Fund, which promoted peace through nonviolent means. The chapter emphasises the emergence of soft power diplomacy in the 1990s, particularly through diaspora figures like Niall O’Dowd, Bruce Morrison, and Chuck Feeney, who helped shape the US government’s involvement in the peace process. Their efforts contributed to the 1994 ceasefire and laid the groundwork for the 1998 Good Friday Agreement. Beyond politics, the chapter highlights how business leaders from the Irish diaspora—such as John Cullinane and members of the Friends of Belfast—fostered economic ties through investment and entrepreneurship. US multinationals and diaspora-driven networks played key roles in reviving Northern Ireland’s economy, especially in tech, finance, and the creative industries. Initiatives like “Hollywood Comes to Belfast” and the US-Ireland R&D Partnership further reflect this synergy. The chapter concludes by acknowledging the blend of ancestral loyalty and economic rationale behind diaspora investment, and underscores the need to sustain these gains through strategic entrepreneurship and cross-border cooperation.