Sixteen years after Platt's resignation, he was elected to the a second time a U.S. Senator from New York in January 1897 and was re-elected in January 1903. This time, he served from March 4, 1897, to March 3, 1909. He was Chairman of the Committee on Transportation Routes to the Seaboard (in the 55th Congress). He was on the Committee on Printing (in the 56th through 60th Congresses), the Committee on Cuban Relations (in the 59th Congress) and the Committee on Interoceanic Canals (in the 59th Congress). He also served on the Republican National Committee.