In 1922, Howse resigned his army commission to enter politics, as regulations at the time forbade political campaigning by members of the regular army. He was elected to the House of Representatives, standing for the Nationalist Party in the Division of Calare. He subsequently represented Australia at the League of Nations Assembly in 1923. In January 1925, Howse was elevated to cabinet by Prime Minister Stanley Bruce as Minister for Defence and Minister for Health. In the defence portfolio his primary responsibility was for repatriation. He was a member of the Australian delegation to the 1926 Imperial Conference in London, but was taken ill and had to resign his portfolios in April 1927. He was kept on in the ministry as an honorary minister without portfolio.