Cox, who is currently head of communications at UK Sport, the agency that funds sport across the UK, replaces Sophie Bradley, who was head of PR and communications at the club until last month. Bradley is now director of PR for sport, fitness and lifestyle at Speed Communications, the UK's 54th largest PR agency.
Cox will work alongside the club's current head of media relations, Max Fitzgerald, handling corporate communications in a role that he is expected to take up early next year. Both will report to Tara Warren, executive director of marketing and communications.
West Ham has repeatedly found itself under the media spotlight recently, with clashes and violence between its fans and Chelsea supporters marring last month's EFL Cup tie between the two clubs.
In the wake of that game, the club's vice-chairman Karren Brady condemned the actions of offending supporters, via a series of tweets.
Fantastic result last night. The team were exceptional & atmosphere electric. Shame that a few marred the occasion. 1/3— Lady Brady (@karren_brady) 27 October 2016
#WHUFC and London Stadium have today been identifying all of them and we will be issuing banning orders. 2/3— Lady Brady (@karren_brady) 27 October 2016
Football doesn't want these people & with over 55,000 supporters on our season ticket waiting list we certainly don’t need them at #WHUFC— Lady Brady (@karren_brady) 27 October 2016
Following the unrest, the club's PR team communicated with stakeholders and fans, issuing a statement of intent almost immediately after the game had ended, saying it and the owners of the stadium "unreservedly condemn the behaviour of individuals involved in incidents during this evening's fixture with Chelsea".
"Whilst quickly brought under control, the Club, in line with its clear zero-tolerance policy, will work closely with London Stadium 185, the Metropolitan Police Service and Chelsea to identify the individuals involved."
The statement went on to say: "All stakeholders are united in their determination to pursue not only stadium bans but also criminal prosecutions against any individual found to be involved in incidents of disorder, where the evidence merits this."
West Ham have also updated their stadium policy and have introduced a new five-point security plan, which includes a zero-tolerance banning policy and larger segregated area between home and away fans.
Following a lengthy PR battle against a rival bid from Tottenham Hotspur, West Ham's arrival in what was the central venue for the 2012 London Olympics and Paralympics caused controversy, in part thanks to questions of whether it provided a good deal for the public.
Recent reports have alleged that costs of converting the stadium for football use have overrun by more than £50m, which has prompted Mayor of London Sadiq Khan to order an investigation.
West Ham has chosen not to comment on the allegations, and is yet to formally comment on the appointment of Cox.