Under the arrangement, the Whiteley-based firm will sponsor the Milton Stand at Fratton Park for two years, meaning Pompey fans see OneCom’s familiar blue and white branding at every home game.
The arrangement will also see OneCom given exclusive rights as a supplier of mobile telecoms for the community-owned club.
As well as supporting Portsmouth Football Club as a main sponsor, OneCom will continue to pour money into the club through its Pompey OneCommunity scheme.
The scheme sees fans offered a free telecoms audit to help them save money, and for everyone who takes services from OneCom, the company donates money to the Supporters Trust.
Darren Ridge, Chief Executive of OneCom, said: “We have, for some time, been an official partner of Pompey for telecommunications and have enjoyed supporting the club with initiatives such as Pompey OneCommunity.
“Like all Pompey fans, I’m very proud of what has been achieved through community ownership and I am glad that we are able to help the club and the Supporters Trust in this way.
“This new two-year arrangement significantly steps up our involvement in the club and we are very proud to now refer to OneCom as the official main sponsor.”
Pompey’s Commercial and Marketing Manager Micah Hall said: "We are delighted to welcome OneCom as our sponsors of the OneCom Milton End. We have enjoyed an excellent relationship with OneCom over the last year as they have brought very substantial sponsorship revenues to Portsmouth FC and great deals on mobiles and landlines to our fans.
“We now look forward to building on that relationship over the next two years to the benefit of all parties. We would like to thank OneCom for their incredible support.”