"Leigh is more than capable of being a Lion if he holds his form," said Jenkins, who kicked the Lions to victory the last time they visited South Africa, before also touring Australia in 2001.
"He isn't a massive guy, but he reminds me of Shane Williams because their strengths and ability to play are incredible.
"He's a quality player and was outstanding again last weekend against Gloucester."
Jenkins, who has helped Halfpenny with his impressive goal kicking, believes the youngster's age won't count against him when it comes to Lions selection, although he admits form over the coming weeks, as opposed to the season so far, will be the crucial factor when it comes to making Ian McGeechan's final squad.
"I don't think it's ever too early to be a Lion," added Jenkins.
"A lot of selection issues will depend on how Wales go in the Six Nations."
If Wales can repeat the form they showed in last year's competition, then Halfpenny could well be making his way to South Africa in the summer.