Omar confirmed her appointment to the House Foreign Affairs Committee in a press statement on Thursday, adding: "We need to reign in arms sales to human rights abusers like Saudi Arabia."
The committee oversees bills and investigations related to US foreign affairs, such as foreign aid and exports to other countries.
It also has to power to boost or reign in US exports of military equipment and technology to other countries, such as Saudi Arabia.
President Donald Trump's administration has come under congressional pressure to condemn Saudi Crown Prince Mohammed bin Salman for the death of journalist Jamal Khashoggi last October. Riyadh has continually sought to distance its leadership from the murder.
But Trump has repeatedly refused to jeopardize his relationship with the Saudi royal family, opting instead to tout the US and Saudi's cozy relations, lucrative arms deals, and low oil prices.
Omar's appointment to the Foreign Affairs Committee also comes after academics and media outlets connected to Saudi Arabia repeatedly tried to smear her even before she joined Congress.
Saudi-owned media outlets, such as Al Arabiya and MBC radio station, reported stories accusing Omar of being a secret member of the Muslim Brotherhood and part of an Islamist faction to control Congress, Foreign Policy pointed out last month.
Riyadh likely launched this media campaign because Omar, as a Muslim woman, could challenge the US' relationship with Saudi Arabia, HuffPost's Akbar Shahid Ahmed reported .
Omar, who fled Somalia as a refugee in 1991, said in a Thursday statement: "As someone who has seen firsthand the havoc wreaked by war, I am proud to serve on the committee that is responsible for overseeing our country's and this President's actions abroad."
"We need to use the committee's human rights jurisdiction to hold the President accountable for deaths in detention centers on his watch. We need to investigate how foreign governments and their lobbyists have violated our laws," she said.
"And we need to reign in arms sales to human rights abusers like Saudi Arabia," she said.
It is rare for freshman representatives to join high-ranking congressional committees like this. New York Rep. Alexandria Ocasio-Cortez, also a first-year congresswoman, secured a spot on the powerful House Financial Services Committee this week.