Lennon was part of the Irish team that won their first European Championship title at the European Show Jumping Championships in Aachen.
In February, Lennon traveled to Gothenburg in Sweden for the CSI5*-W Show. He won the opening competition, a 1.40m class, riding Tolett. Lennon then topped-off the weekend by finishing 3rd in the Rolex FEI World Cup Qualifier on Woods Rosbotham's gelding, Hallmark Elite. This secured him a place in the Final in April.
Lennon traveled to Geneva for the Rolex FEI World Cup Finals. In the Credit Suisse Grand Prix qualifier on Day 2, he partnered Tolett to finish 4th. On Day 3, Lennon directed Tolett to finish second in the Accumulator class - Prix Tribune de Genève. In Part 1 of the World Cup he was clear in a time of 75.73 seconds, this left him lying in 13th position. After Part 2, Lennon climbed to 11th after having 4 faults in the first round. Having jumped one of only three clear rounds in Part 3, he secured 5th position overall - only 4 faults off the eventual winner - Marcus Ehning.
On the 3rd of May, Lennon won the second leg of the Showjumping Ireland Premier Series Grand Prix in Coilog EC with the eight year old Vampire.
For the last weekend of May, Lennon travelled to the CSI3* of Norten-Hardenberg, Germany. On Friday, he finished 4th in the 1m50 'Preis der Hardenberg-Wilthen AG' with Tolett, the pair also finished 3rd in the 1m50 'Gothaer Trophy'. He then jumped 'Hallmark Elite' in the final class - a 1m45 jump-off. They were one of 13 clears to go through to the jump-off where they had 4 faults to finish 10th.
At the beginning of July, Lennon travelled to the CSIO5* in Falsterbo, Sweden as part of the Irish squad. On day 1, with Tollet, he finished 2nd in the first of two JMS Derby qualifiers. That evening, he steered Woods Rosbotham's Hallmark Elite to 5th place in the Grand Prix qualifier - a 1m50 one round class. In the 5th leg of the Meydan FEI Nations Cup, which was won by the home team, Ireland finished 5th on 24 faults: Dermott Lennon (Hallmark Elite) 4/12, Jessica Kuerten (Castle Forbes Myrtille Paulois) (8)/(12), Shane Breen (Carmena Z) 4/4, Denis Lynch (Nabab's Son) 0/0.
- Rolex FEI World Cup Final Part III - CSI5* World Cup Final Geneva, Switzerland, (Hallmark Elite)
- 3rd, Rolex FEI World Cup Qualifier - CSI5*-W Gothenburg, Sweden (Hallmark Elite)
- 3rd, FEI World Cup Qualifier - CSI4*-W Toronto ON, Canada (Hallmark Elite)
- 4th, FEI World Cup Qualifier - CSI4*-W Syracuse NY, Canada (Hallmark Elite)
- Grand Prix - CSI3* Vilamoura, Portugal, (Hallmark Elite)
- Grand Prix - CSI2* Towerlands, Great Britain, (Hallmark Elite)
- FEI World Equestrian Games (Liscalgot)