A former assistant at Go Ahead Eagles and Zwolle, Maaskant was named head coach of RBC Roosendaal for the 1999–2000 season. He worked there for three years, before joining Go Ahead Eagles. Maaskant worked in Deventer for seven months, came back to Roosendaal, and then moved on to Willem II in the summer of 2004. He was sacked on 21 November 2005 and replaced by Kees Zwamborn. On 4 January 2006, Maaskant was re-instated as the manager of RBC Roosendaal, as the successor of Dolf Roks. Maaskant was sacked in 2007 and signed a one-year contract with MVV Maastricht for the 2007–08 season with an option to extend it for two more years. In February 2008, he left MVV and signed for NAC Breda to be the auxiliary coach of Ernie Brandts. In the summer of the same year, as soon as Brandts left the Bredase club, Maaskant took the spot.
Maaskant had two rather successful seasons at NAC Breda. In the first season, NAC qualified for the UEFA Cup. In Maaskant's second season at NAC, the club nearly missed play-offs for the UEFA Cup. From May 2010 onwards, it appeared that NAC had financial problems. Directly afterwards, he raised his concerns via the press[1][2] and Maaskant wasn't able to afford new players.
On 21 August 2010, NAC and Maaskant made public that he would leave NAC Breda for Polish football club Wisła Kraków, signing a two-year deal.[3] Maaskant won the Polish championship in his first season at Wisła Kraków. However, he missed the qualification to the 2011–12 UEFA Champions Leaguegroup stage. On 7 November 2011, a day after Wisła's first away loss against city rival Cracovia since 28 years, Wisła Kraków announced that they had parted ways with Maaskant.[4]
On 23 May 2012, Maaskant signed as head coach for Groningen.[7] This was possible because of a clause in his Dutch Lions contract, that allowed him to leave early.[8]
Groningen announced on 11 March 2013 that it would not be renewing its one-year contract with Maaskant.[9]
In June 2013, Maaskant signed a one-and-a-half-year contract with Belarusian side Dinamo Minsk.[10]
In January 2014, Maaskant signed a one-year contract with the Columbus Crew in the Major League Soccer to be their assistant coach.
On 2 January 2015, it was announced that Maaskant had returned as head coach of Eredivisie side NAC Breda.
On 25 March 2017, Maaskant was appointed manager of Go Ahead Eagles for the remainder of the 2016–17 season.[11]
Maaskant was appointed director of football at Almere City on 24 March 2018.[12] He left the position at the end of the 2018–19 season to become manager of VVV-Venlo.[13]
