The Keeping Up With the Kardashians star, who has not confirmed her pregnancy herself, was spotted walking in the city while wearing light blue high-waist, ripped skinny jeans tucked into thigh-high black boots, a black belt, a black top and a full-length black wool coat.
It marked a rare public appearance for Khloe, who has kept out of the spotlight more in recent weeks. In late September, multiple sources told E! News that the 33-year-old is expecting her first child with 26-year-old Cleveland Cavaliers player Tristan Thompson, her boyfriend of more than a year.
During their trip to San Francisco, the Kardashian sisters visited Alcatraz and also rode a cable car in the city. Later on Sunday, Kim returned to Los Angeles to take part in the star-studded One Voice: Somos Live! A Concert For Disaster Relief telethon.
Khloe had also made a rare public appearance earlier this month at the 1-year anniversary of her Good American denim line at Nordstrom in Century City, California, wearing a black jacket with a Chanel belt, a pair of leather pants and Louboutin heels.
According to People, she said to the crowd at the event, "My weight fluctuates all the time and I love that at any size I feel comfortable. When I was bigger and wore bigger clothes I looked even bigger. I love embracing my curves no matter what size I am."
Khloe and Tristan have kept mum about her pregnancy but have dropped what could be interpreted as several hints about it on social media.
In addition, on the season 14 premiere of Keeping Up With the Kardashians last month, Khloe answers a question about having kids with Tristan, to which she responds, "I honestly wish we could just be together and like when it happens, it happens. When you make plans, God laughs."
"But I feel like all of us are so close that all of our children are kind of brought up in the same vicinity, or one block over, that everybody's kind of there for each other," he said. "I don't really need to give advice per se because, we are right there. It's not like long-distance, 'hey, maybe you should try this?' Everybody so hands-on that I feel like it will happen within time. So no real advice in that sense."
Watch a brand new episode of Keeping Up With the Kardashians Sunday at 9 p.m., only on E!