Carlin, 28, missed London 2012 because of illness, but has since won European and Commonwealth gold medals.
American Katie Ledecky is favourite for the 400m and 800m freestyle, but 1988 100m breaststroke champion Moorhouse believes Carlin can get on the podium.
"There's a medal up for grabs and Jazz is capable of doing it," he said.
"I think she'll have to drop [her time] a little bit more - she'll have to have the swim of her life.
"She'll be in the final so, if she's in the final, the question is if she can push for medals."
The 19-year-old Ledecky has dominated women's distance events since London 2012 when, as a 15-year-old, she took the 800m gold medal.
Moorhouse expects Ledecky to win and for the others to be racing for silver and bronze.
"I think what we all know is that particularly in the 800m is you have to swim your own race you have to pace it and not worry too much about what's going on around you but I think she needs to be in the fight," added Moorhouse.
"I'd like to see her get a really good qualifying time to get in the middle [lanes] - I'd like to see her be in lanes three or five if Ledecky's going to qualify in four, and then she's amongst the race."
Moorhouse has been impressed with the progress of Chloe Tutton in 2016.
The 20-year-old from Ystrad Rhondda came to prominence when she broke the national 100m breaststroke record at the British Championships in April and has since won a European gold medal as part of the British medley relay team.
Like Carlin, Tutton will be up against a dominant opponent in the shape of reigning Olympic champion Ruta Meilutyte, the Lithuanian who is based in Plymouth.
"Chloe's got a really strong time from the European Championships earlier this year and only her and her coach will know what she's got up her sleeve - how much more she can drop," said Moorhouse.
"I think she's still got time to improve on - the question is whether from May until now is enough time to do anything dramatic, but she's got a chance of a medal.
"She's not got to be intimidated, she's got to go out there and think it's the best year of her life really - which it probably is at the moment.
"The competition is tough, but if she can just be confident, not be worried about what everybody else is doing and just stick to what she's been doing she'll be great."
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Welsh swimmer Jazz Carlin has a realistic chance of winning a medal in Rio if she has "the swim of her life", Adrian Moorhouse says.