After playing for Waikato in their championship winning 2006 Air New Zealand Cup side, Leonard was selected for the Chiefs in the 2007 Super 14.

Leonard had a successful Super 14 where he played for Byron Kelleher who missed the first seven rounds of the competition to participate in the All Blacks reconditioning programme.

He was one of only two uncapped players named in the squad, and All Blacks coach Graham Henry said of Leonard's selection "Brendon [Leonard] has been the best attacking scrum-half in the Super 14 this season and has forced his way into the side based on form.

On 12 August 2013, Leonard left New Zealand as he signed for new Italy franchise Zebre in the Pro12 from the 2013–14 season.

[3] On 22 January it was announced Leonard had signed for the Ospreys, mainly to provide experienced cover for Welsh international Rhys Webb during the 2015 Rugby World Cup.