The distinctive Fender Squier Stratocaster was taken along with a number of other items when the silver Peugeot was left outside a house in Blenkinsop Way in Middleton last weekend.
Owner Martin Cruse-Stoddart said the guitar, given to him as a 15th birthday present, was his most valued possession for sentimental reasons.
“After lapsing for a few years, I’ve just started guitar lessons again in the last couple of months,” the 46-year-old said.
“The reason it was in the car is that I’d been for a lesson at Leeds Music Academy.
“Like a fool I left items in the car unattended, somewhere I thought it was safe.”
Martin lives in Wakefield but had been staying with a friend for the night.
He said that he was devastated to have lost the guitar he had owned for more than 30 years, adding: “All I care about is getting the guitar back.”
The guitar is black with a white scratch plate and is covered in stickers including The Terminator near the bridge and a Judge Dredd sign on the head stock. It has some deep scratches on the back of the body, and a tiny gouge on a fret.
The guitar was in a black padded Road Runner case with VOX AC30 plug in headphone amp in the pocket. Also taken were a Lenovo Thinkpad, Kindle Fire HD, Nook + e-reader, Converse sunglasses, O’Neil prescription glasses, Police silver mirror sunglasses and a Bench parka.
Police said the thieves had initially tried to force open one of the car’s locks but eventually gained access by smashing the front passenger window.
It happened some time between midnight and 11am on Sunday, May 6.
Anyone who is offered the guitar is urged to call 101.