Kenyatta, son of Kenya's first president since independence in 1964, was sworn into office Tuesday. He secured a narrow victory over former Prime Minister Raila Odinga, who challenged the outcome of the election in Kenya's high court.
Ruto called on Kenyans to work together in the spirit of unity as the new government worked to address development issues.
"We will work together irrespective of how you voted," he was quoted by The Daily Nation newspaper in Kenya as saying. "We will serve all of you equally."
Kenyatta cleared the 50-percent margin needed to win by less than one percent.
Odinga's challenge to a 2007 sparked political violence that left more than 1,000 Kenyans dead. Kenyatta and Ruto were indicted by the International Criminal Court for allegedly playing a role in the post-election violence.
Both men deny the charges. Kenyatta is slated to appear before The Hague in July. He said he believes the charges will be dropped because of similar developments in related cases.