South Shields Cricket Club scooped the £18,000 deal with town-based petsupermarket.co.uk, run by Mark Berriman.
Under the three-year deal, all players will carry the firm's logo on their shirts, and advertising hoardings will be visible around the ground in Dean Road.
Officials say they hope the announcement will attract more sponsorship, to help develop the club as it begins competing at a higher level.
Chairman John Pack said: "We never dreamt of finding a sponsor at this level in local cricket. It has really helped us move forward. I think it's great that a successful young person like Mark is only too happy to help his local club and invest in his home town."
He added: "Mark even turned down the offer of exclusivity on the shirts so other businesses could get involved."
Last season was the most successful in the club's history, with the first team earning promotion after winning the Durham Senior League unbeaten.
The second team also won its league, and the combined efforts of the junior teams took top honours by winning the overall championship title.
Mr Berriman, 27, managing director of the web-based firm, said he was attracted to the club because of the work it does with youngsters.
He said: "While not a big cricket fan, I think it's great that the club does so much for young people, providing a good forum for them to develop through the juniors system.
"All you hear about is the bad things young people and teenagers get up to, but there is so much good work going on, and the club represents a perfect example of this."
He added: "What the club has recently achieved is magnificent. I hope other businesses get behind it to ensure the teams go from strength to strength."
Mr Berriman, of South Shields, launched petsupermarket.co.uk three years ago, after struggling to buy the right food products for his dog on the internet.
Its turnover leapt from just under £500,000 in its first year to £1.6m in its second financial year.

By DAVID MacLEAN
david.maclean@northeast-press.co.uk