Waving Turkish flags and whistling, fans made their way to the stadium after 44 people were killed on Saturday in an attack claimed by Kurdish militants.
Besiktas was playing on Wednesday against Kayserispor in a Turkish cup match at its new arena, on the shores of the Bosphorus.
A mournful silence was broken by fans making their way to the game, chanting "martyrs never die, homeland not divided" -- slogans of solidarity and patriotism rather than the usual team slogans, an AFP correspondent said.
Later inside the stadium, the slogans were repeated as fans sought to pay tribute to those killed and show a united front.
A car bomb exploded on Saturday outside the stadium and less than a minute later, a suicide attacker blew himself up next to a group of police officers at a nearby park.
Some 37 police officers and seven civilians were killed in the blasts claimed by the Kurdistan Freedom Falcons (TAK), which is seen as a radical offshoot of the outlawed Kurdistan Workers' Party (PKK) listed as a terror group by Turkey and its Western allies.
One of the Besiktas coaches Veyiz Oguz said Turkish football fans were united in mourning.
"Right now, Galatasaray fans are with us, Fenerbahce fans are with us," referring to Istanbul's two other big teams.
- 'All united'-
Kayserispor fan Mehmet said he came all the way from the central Turkish city of Kayseri for Wednesday's match.
"Today, we Trabzonspor fans, Besiktas fans, Galatasaray fans are all united," he told AFP.
"God willing these incidents end and our matches can occur peacefully," he added.
Seyma, a female fan of Istanbul top flight Galatasaray, said: "Today is the day to show unity," adding that she hoped "friendship will win today. Turkey will win."
Besiktas midfielder Olcay Sahan took two Turkish police officers by the hand to the field and the audience applauded, an AFP photographer said.
Besiktas coach Senol Gunes and goalkeeper Tolga Zengin also laid wreathes on the players' benches.
A sea of flowers, including carnations coloured the red and white of the Turkish flag, have been left outside the stadium, along with scarves from all of the Turkish teams. An imam recited from the Koran at the site on Wednesday evening.
Besiktas said this week that money from tickets sold for Wednesday's match would go to victims' families.
Anil Akbulut, a fan of one of the other Istanbul giants Fenerbahce, said what mattered was not the match but the solidarity.
"What we experienced was painful," he said. "It doesn't matter which team I support. I know that the ticket proceeds would go to martyrs' families and that's why I came with my fiancee to watch the game."
"We invited fans from all teams," Hakan Ozkose, a Besiktas board member, told AFP. "We made the decision in order to show we are one heart against terror."