Born in
Groningen,
Groningen,
Netherlands, Slagter currently resides in
Leeuwarden,
Friesland,
Netherlands. Slagter won the
Tour Down Under, his greatest career achievement. Slagter won the third stage after attacking on the finial climb, cresting it alone. He was joined by three riders on the descent, and with the
peloton on their heels, Slagter out-sprinted the group. On the fifth stage, he gained the orange jersey; finishing atop Old Willunga Hill in second position, behind Australian
Simon Gerrans (), the
defending champion. On the final stage, Slagter successfully defended his lead, with Spaniard
Javier Moreno () earning second place, seventeen seconds in arrears. In August 2013, Slagter signed with the squad, penning a two-year deal.
Garmin–Sharp (2014–2017) 2014 At
Paris–Nice, Slagter won stages 4 and 7. He then went on to finish 2nd in the Spanish one-day race
GP Miguel Induráin. His last race before his classics campaign was the
Tour of the Basque Country in which he finished 13th. At
Liége–Bastogne–Liége he finished 6th, his best result ever in a monument. Before that he also finished 5th in
La Flèche Wallonne. Slagter rode the
Tour de France, and finished 9th on stage 16 to
Bagneres-de-Luchon. After the Tour, he rode the
Clásica de San Sebastián. and finished just outside of top 10, in 14th place. He rode the Canadian World Tour classics,
Grand Prix Cycliste de Québec, and
Grand Prix Cycliste de Montréal, where he finished 11th and 12th respectively.
2015 Slagter's best result during the first part of the 2015 season, was finishing 9th in
La Flèche Wallonne. He rode the
Tour of Alberta, and won 2 stages during the race. He then rode the Canadian World Tour classics and finished 4th in
Québec and 10th in
Montréal.
Team Dimension Data (2018–2019) In August 2017, Slagter signed a contract with . At the
Tour Down Under, Slagter finished 3rd overall, in his first race for the team. His best result during the classics period was 12th at
La Flèche Wallonne.
B&B Hotels–Vital Concept (2020) After one season with , Slagter announced his retirement in November 2020; he intended to become a tractor salesman. ==Major results==