Following his recovery from injury, Kelleher was able to play more regularly in his second season. He played 18 times between the Pro14 and the Challenge Cup, scoring three tries. In March 2018, it was announced that Kelleher had signed an extension to his Connacht deal. He had his most successful season with the side in 2018–19 season, appearing 17 times in the Pro14 and scoring five tries. Kelleher also started four of the team's six group games in the Challenge Cup and the quarter-final against Sale Sharks. In January 2019, it was announced that Kelleher would leave Connacht after three seasons with the province. He made a total of 54 appearances in his time with the side, scoring 14 tries.