"They have a lot of love and respect for each other," one insider told E!.
The source said the long distance and their demanding schedules "made it really difficult to maintain a relationship."
Pete has been spending time in Australia while he films a new movie while Kim is home with her kids North, Psalm, Chicago and Saint.
Kim and Pete's romance was first confirmed back in November. The sparks started after the reality star mogul made an appearance on Saturday Night Live the month before.
At the time, a source said, "She is telling some people they aren't super serious but she isn't seeing anyone else... She's trying to not make a big deal about it but is super into him."
The couple was inseparable for several months after their relationship started. Kim was spotted making trips to New York to hang out with Pete while he flew to Los Angeles for quality time.
The relationship caused drama with Kim's ex-husband Kanye West who publicly attacked Pete. The beef lead to Pete leaking texts he sent to Kanye asking him to "calm down."
The comedian wrote, "Kim is literally the best mother I've ever met. What she does for those kids is amazing and you are so f------ lucky that she's your kids mom. I've decided I'm not gonna let you treat us this way anymore and I'm done being quiet. Grow the f--- up."
Kim visit Pete overseas in July after having been apart for several weeks. "They enjoyed a long weekend together," a source told People earlier this week. The insider said Kim was "excited that he will be back in the U.S. soon."
Based on the timing, it appears Kim and Pete spoke in the past couple of days and decided the relationship wasn't working out for either of them.
Kim and Pete have yet to make an official comment.