Pickton listened to the verdict with his head bowed and later smirked. He will receive life in prison and will not be eligible for parole for at least 10 years when he is sentenced on Tuesday.
The jury of seven men and five women took 10 days to reach their verdicts.
Family members and friends sobbed as they gathered for a candlelight vigil outside the courthouse after verdicts were returned.
Lead prosecutor Michael Petrie called the verdicts "a very good result".
Before the jury began deliberations on November 30, judge James Williams reviewed the transcript of a videotape with them in which Pickton is heard telling an undercover police officer that he had planned to kill one more woman before stopping at 50, taking a break and then killing another 25 women.
"I was going to do one more; make it an even 50," Pickton told the officer, who had been planted in the accused killer's cell and gained his trust.
The judge also reviewed testimony of prosecution witness Andrew Bellwood, who said Pickton told him how he strangled his alleged victims, butchered them and bled them before feeing their remains to his pigs.
Pickton has been charged in the slayings of 26 women, but almost 40 others are on a police list of missing women. The investigation into their disappearances is ongoing.
Prosecutors said Pickton will be tried on the 20 other murder charges later, but no date has been set.
Pickton has been in jail since his arrest in February 2002.
Jurors had the option of finding Pickton guilty of first-degree murder, second-degree murder or manslaughter or not guilty on any of the six counts.
Second-degree murder is a lesser charge that means a murder was not planned.
First-degree murder, which means a murder was planned, also carries a mandatory sentence of life in prison but does not offer parole eligibility for 25 years.