(From left) PC Keith Palmer, Kurt Cochran and Aysha Frade all died in the attack
PC Keith Palmer, 48, was stabbed as he tried to stop the attacker in a courtyard outside the Houses of Parliament.
He was an unarmed member of the Parliamentary and Diplomatic Protection Squad who had served for 15 years.
"Keith will be remembered as a wonderful dad and husband," his family said in a statement.
"A loving son, brother and uncle. A long-time supporter of Charlton FC. Dedicated to his job and proud to be a police officer, brave and courageous. A friend to everyone who knew him.
"He will be deeply missed. We love him so much. His friends and family are shocked and devastated by his loss."
PC Palmer, who had a five-year-old daughter, joined the Parliamentary and Diplomatic Protection Command in April last year after serving in the Territorial Support Group (TSG) based in Catford but working across London. He had previously been based in Bromley borough between 2002 and 2009.
Kurt Cochran from the US state of Utah was in London as part of a holiday in Europe to celebrate 25 years of marriage to his wife Melissa, who was seriously hurt in the attack.
In a statement, Mrs Cochran's family said they were "heartbroken" by the news of Mr Cochran's death.
"Kurt was a good man and a loving husband to our sister and daughter, Melissa," they said.
They said Melissa had received serious injuries in the attack and was being treated in hospital. The couple had been scheduled to return to the US on Thursday.
"We express our gratitude to the emergency and medical personnel who have cared for them and ask for your prayers on behalf of Melissa and our family. Kurt will be greatly missed," they added.
Aysha Frade, who worked at DLD College London, close to Westminster Bridge, also died in the attack.
She was a British national whose mother was Spanish, the Spanish foreign ministry said.
Ms Frade lived in London with her two young daughters and husband, according to Spanish media reports.
Her father was of Cypriot origin, while her mother was from the Galician town of Betanzos, where her two sisters run an English school, the Voz de Galicia reports.
The principal of the independent sixth form college said she worked in the administration team and described her as "a highly regarded and loved" member of staff.
"She will be deeply missed by all of us," Rachel Borland added.