Bulldogs chairman Kevin Nicholas and Rams counterpart Mark Sawyer led the tributes by laying sunflowers on the halfway line, followed by a host of dignitaries.
Birstall man and Bulldogs fan Bernard Kenny, and his family, were guests of honour at the club.
Mr Kenny was himself injured after he rushed to try and save Mrs Cox’s life when she was shot and stabbed in Birstall town centre two weeks ago.
Other dignitaries to pay tribute to Jo included Dewsbury MP Paula Sherriff, Leeds North West MP and vice president of the Leeds Rugby Foundation charity Greg Mulholland, St Helens MP Marie Rimmer, RFL chief executive Nigel Wood and Batley Bulldogs chaplain Derek Ventress.
Local singer Paul Egan paid his own tribute with a moving rendition of Abide With Me.
Mr Nicholas paid tribute to Jo in the matchday programme, which saw all proceeds donated to the Jo Cox Memorial Fund, set up in her memory.
Mr Nicholas said: “As a club and as a community we are proud of (Jo) and everything she did and was trying to do for us and others in less fortunate circumstances.
“She was supportive of our club and her smile, enthusiasm and love of life were infectious and heartwarming.
“We are also proud of the courage shown by Bernard Kenny in trying to help her.
“Jo and Bernard are people that give us hope and reassure us in difficult times that there are good people about which need to outshine the bad ones.”
Bulldogs coach John Kear praised to the club for the way they paid their respects in the build up to Sunday’s game to Jo, adding: “ I think it was a really respectful way of paying tribute and I thought it was very touching and gracious.
“It reflected how highly Jo was thought of not just at this club but within the community as a whole.
“Dewsbury also played their part too and although there is rivalry within a very small area, we are all part of this area and obviously the loss have affected everybody.”