[6][7] While at Trinity he was president of the University Philosophical Society (The Phil) and editor of Piranha, a satirical college magazine.

According to former Web Summit director David Kelly, as a senior female IDA executive gave a short welcome speech, Paddy Cosgrave stood beside her “slow clapping”.

[25] The Web Summit has also been the subject of several controversies under Cosgrave's stewardship, including its move from Dublin to Lisbon,[26] the organisation of a dinner at Portugal's National Pantheon,[27] and the invitation of Marine Le Pen as a speaker, which was subsequently withdrawn.

[32][33] On 30 March 2020, Cosgrave posted a tribute on Twitter to the "4 nurses in Ireland who fought so hard for so many patients, but who themselves fell ill, and have now passed.

Phil Ni Sheaghdha, general secretary of the Irish Nurses & Midwives Organisation (INMO), accused Cosgrave of "scaremongering".

[36] Also in 2020, Cosgrave was criticised for using what some inferred as sectarian and pejorative language in calling Neale Richmond a "Castle Catholic".

Although he remained firm with his previous condemnation, he later on apologized,[40][41] and subsequently resigned as CEO of Web Summit on 21 October after companies like Intel, Siemens, Google, Amazon and Meta withdrew from the 2023 event.

[45] In November 2021, an Irish High Court case was filed while the Web Summit conference was underway in Portugal, marking an intensification of the legal battle between the two co-founders of the event.

Paddy Cosgrave has been accused of oppressing a minority shareholder, attempting to engage in blackmail against a co-director, and hacking a rival Irish events company.

[46][47][48] In the same month, Cosgrave was accused by a former director of Web Summit of regularly demeaning and chastising staff members.

[50] In April 2022 Cosgrave was sued by a former Web Summit PR executive Mark O’Toole in the Irish High Court.