Patterson will join Michael Birch and Wayne Boyd in a McLaren 720S GT3 EVO in the multi-class series.
Bronze-rated Birch is an experienced historic racer but has also raced LMP2 cars.
Gold-rated Boyd has a heap of knowledge in sports cars and GT machinery and has been a staple of the United Autosport ranks for nine seasons.
Patterson, an FIA Silver-rated driver, will continue his journey with United Autosport after narrowly missing out on a 24 Hours of Daytona win.
“I’m so excited to be racing the McLaren in the European Le Mans Series with United Autosports,” said Patterson.
“After starting the year in LMP2 at Daytona, it’s fantastic to continue with the team as I transition to LMGT3 in McLaren’s first ELMS season in many years.
“The team has worked incredibly hard throughout the past WEC season, and I think that effort was evident in Qatar. Alongside Michael and Wayne, we’ll be giving it our all to secure the best results for the team. I’m looking forward to Barcelona.”
The European Le Mans Series features LMP2, LMP3, and GT3 (called LMGT3) cars on the same grid, with a variety of GT brands including Porsche, Lamborghini, Ferrari, and Mercedes to name a few.
The title winner of the European Le Mans Series in LMP2 and LMGT3 is granted a 24 Hours of Le Mans entry for the following season.
“It is very exciting to see our new LMGT3 programme in the European Le Mans Series coming together,” said Richard Dean, United Autosports CEO.
“We have learnt an incredible amount about the McLaren over the past 18 months, which means we are building on solid foundations for our ELMS LMGT3 debut.
“I think that Michael, Garnet and Wayne will make a fantastic team, and I look forward to seeing them in action together in Barcelona.”
The European Le Mans Series begins in Spain with a four-hour race at Circuit de Catalunya-Barcelona.
That will be followed by races at Paul Ricard, Imola, Spa-Francorchamps, Silverstone, and Portimao.
