The 35-year-old suspect was detained in the centre of the city a day after the stabbing which caused panic as shoppers hunted Black Friday bargains.
Police had earlier said they were investigating "several scenarios" and that it was "too early to speculate" about whether there was a possible terror motive.
The attack happened just hours after a convicted terrorist stabbed two people to death in London.
"Following the stabbing incident in Grote Marktstraat, a 35-year-old man has just been arrested in the centre of The Hague. The man has no fixed place of residence," police said on Twitter.
"He will be transferred to a police station where he will be questioned."
The victims were a 13-year-old boy and two 15-year-old girls, none of whom knew each other, police said. They were all treated in hospital but released overnight.
The male attacker ran off after the stabbings at a department store in the city centre, triggering a huge manhunt involving police helicopters.
Images on social media showed shoppers running in panic away from the scene, on a night time retail street lit by Christmas fairy lights.
Two teenage girls came running into the store after being stabbed, broadcaster NOS quoted witnesses as saying.
'Screaming and running away'
"I saw two girls screaming and running away. A man fled. He jumped very athletically over benches to get away. He looked like a cheetah," one witness told NOS.
"People were trying to get away. But that didn't work. I was shocked."
Police forensics officers were seen examining a knife found at the scene overnight.
"It's a little too early to speculate about that kind of thing," police spokeswoman Marije Kuiper told AFP earlier when asked about a possible terrorist motive, adding that investigators were still looking at several possible scenarios.
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