The number of attendees in the events on the day exceeds one hundred thousand. On the day, the Helsinki Medal is awarded to noteworthy citizens by the city council.
The event was started by mayor Lauri Aho and secretary of the Helsinki Society Jorma Waronen in the late 1950s. The first Helsinki day was celebrated in 1959 on the 409th anniversary of the founding of Helsinki.
The number of attendees at events on Helsinki Day already exceeded ten thousand in the early 1960s. In the same decade, the events were made more entertaining and diverse. Main events, such as ice hall concerts, were added. As the day gained popularity, the association of neighbourhood societies wanted to expand the celebration to a full Helsinki Week in the late 1970s, but the city council denied permission. Nowadays, Helsinki Week, culminating on Helsinki Day, has been established, and it is directed by the event unit of the Helsinki city council.
Since the 1990s, various units of the city council, organisations and corporations have organised events on Helsinki Day. The free-of-charge "Kaivari" concert in Kaivopuisto is probably the best known among the public.