Washington had announced its intentions to re-establish its presence in the Pacific nation early last year, following concerns over China's security pact with the Solomons and greater interest in the Pacific.
US Secretary of State Antony Blinken said the opening of the embassy "symbolises a renewal relationship" between the two countries.
Blinken said it also highlights the strength of their commitment to their bilateral relations, the people of Solomon Islands, and their partnerships in the Indo-Pacific region.
He said the US values its shared history and sacrifice with Solomon Islands, and looks forward to continuing to strengthen its partnership in a range of areas, including economic development, combating the Covid-19 pandemic, and addressing the challenges of climate change.
He added that the re-opening of the Embassy builds on their efforts not only to place more diplomatic personnel throughout the region, but also to engage further with their Pacific neighbours, connect United States programmes and resources.
Meanwhile, the Whitehouse has confirmed Russell Comeau will continue to serve as the interim US Chargé d'Affaires.