Stewart allegedly moved out of the pair's Los Angeles home in July after the revelation that she had cheated on her Twilight co-star with Snow White and the Huntsman director Rupert Sanders.
Other rumours suggested that Pattinson had decided to sell the property and move back to London, though Us Weekly now claims that the pair have chosen to move back in together.
"They are living together and have reconciled," a source claimed.
However, the insider also alleged that Pattinson is "extra-sensitive" and "insecure" at the moment.
The claim comes shortly after reports that the couple spent a weekend together in Los Angeles and rumours that Pattinson is hoping to marry Stewart.
Earlier this month, Stewart dismissed claims that there was tension between her and Pattinson, saying that they are "totally fine".
Photo gallery - Kristen Stewart and Robert Pattinson's relationship: