In a press release, the back-of-the-grid Spanish team said Barcelona born Clos, 23, will take part in “several” Friday morning practice sessions and travel “to every grand prix” in 2012.
HRT’s race drivers for this season are Spaniard Pedro de la Rosa and Indian Narain Karthikeyan.
Clos, on the GP2 grid in the past few seasons and ninth overall last year, ran with HRT at the Abu Dhabi young driver test last November.
The team said he will attend F1’s final winter test in his native Barcelona in March, where HRT is expecting to run its 2012 car for the first time.
“The team has changed a lot since we met in the Abu Dhabi tests and I think it’s a great opportunity and an honour to form a part of this new team,” Clos is quoted as saying.