The 27-year-old Belgian replaces Matt Halliday at the one-car team after the team decided not to extend the Kiwi's initial three-race deal beyond the last event in Houston, and is delighted to be back with the team in a deal that will see him complete the season.
"I have been working hard to get back into Champ Car, and I am very excited to be racing for a team like Conquest," said Heylen.
"The team gave me my first test in Champ Car and now I am looking forward to racing with them. It has been quite frustrating to be watching the first few races of the year from the pits, but now I have a good opportunity to compete with Conquest."
Dominguez dropped by Forsythe
Team boss Eric Bachelart was born in Belgium and is delighted to have a driver from his home nation back in the car, especially with the series racing in the country for the first time, at Zolder, in September.
"I had my first race at Zolder when I was just starting as a driver, and it is something quite special for us to be racing there this year," said Bachelart. "I have raced there many, many times, but this year will be a memorable one no question."
Heylen, 27, drove for Dale Coyne Racing, finishing 14th in the championship with a best finish of fifth at Cleveland.
Halliday joins Conquest
Perera ends Sebring test on top