He became a member of British Cycling's Olympic Academy in 2008, moving with the rest of the squad to live in Tuscany, Italy.

[10] He was described by Cycling Weekly as "the most talented youngster to roll off the Isle of Man production line since his friend and star sprinter Mark Cavendish".

Kennaugh made his grand tour debut in the Vuelta a España, but Sky withdrew following the death of soigneur Txema Gonzalez.

Instead, Kennaugh won the Lincoln Grand Prix before playing a key role as a mountain domestique as Froome and Richie Porte took a 1–2 overall in the Critérium du Dauphiné in June.

However, on the following stage, Kennaugh was involved in a dramatic crash as Ryder Hesjedal,[20] a Garmin–Sharp rider, knocked into him, sending him down a ravine and into vegetation next to the road.

Although Kennaugh was not badly injured, the time lost meant he was unable to follow several subsequent attacks as Froome was left completely isolated.

[22] Kennaugh won the British National Road Race Championships on 29 June, outsprinting Sky teammate Ben Swift in Abergavenny.

Kennaugh won the opening stage of the Critérium du Dauphiné after attacking on the final climb and holding off the charging main field by two seconds on the descent into the finish in Albertville.

[27] Kennaugh lost the race lead after the team time trial on Stage 3, but then helped Chris Froome win the event overall.

In June, he won the National Road Race Championships, distancing Mark Cavendish on the final cobbled climb[28] and becoming the first rider to successfully defend the title since Roger Hammond in 2004.

[30] In September, Kennaugh broke Chris Boardman's time trial record for the 37.73-mile (60.72-kilometre) Isle of Man TT Mountain Course by six seconds, riding a standard racing bicycle.

After riding the Tour Down Under, Kennaugh won the Cadel Evans Great Ocean Road Race in Geelong after attacked from a small group on the final climb and held off the chasers for the 12 kilometres (7.5 mi) to the finish line.

[38] In 2019, Kennaugh joined ITV4's coverage of the Tour de France as a pundit alongside Gary Imlach, following the departure of Chris Boardman the previous year.