Mr Finnigan is a Muggle, the husband of the witch Mrs Finnigan, and the father of Gryffindor student Seamus Finnigan. His marriage to a witch, which was initially kept secret from him, establishes his son Seamus's half-blood status. Though a minor character, Mr Finnigan's presence demonstrates the integration of Muggles into the wizarding world through family ties.
Mr Finnigan married his wife without knowing she was a witch. According to their son Seamus, she did not reveal her magical nature until after they were wed, which came as a “nasty shock” to him. Despite this, he evidently came to accept his wife's world, raising a magical son with her. In August 1994, Mr Finnigan accompanied his wife and son to the Quidditch World Cup final between Ireland and Bulgaria. He and his family were enthusiastic supporters of the Irish National Quidditch Team, wearing large green rosettes and decorating their tent with shamrocks. He was seen by Harry Potter in the Top Box during the match, enjoying the event alongside Ministry of Magic officials and other important guests.
Mr Finnigan is described in his only physical appearance as being “gingery-haired,” a trait he shares with his son, Seamus Finnigan. While little is revealed about his personality, his initial “nasty shock” upon discovering his wife's magical abilities suggests he was unprepared for the revelation. However, his cheerful presence at the Quidditch World Cup years later indicates he grew to be comfortable and supportive within the wizarding world. He appeared to be a good-natured and enthusiastic sports fan.
The surname “Finnigan” is a common Irish surname, an anglicization of the Gaelic Ó Fionnagáin, meaning “descendant of Fionnagán.” The personal name Fionnagán is a diminutive of “Fionn,” which means “fair” or “white.” This surname firmly establishes the family's Irish heritage, which is a prominent part of their identity, most notably through their fervent support for the Irish Quidditch team.