Last month, the Desperate Housewives actress ended her one-year relationship with Cruz, who is the brother of fellow actress Penelope Cruz.
The pair were seen arriving and leaving the Chateau Marmont in West Hollywood, reports X17.
"Over the course of the evening, Eva and Eduardo were holding hands and whispering to each other, and things definitely appear to be back on between them," a source claimed.
News of the ex-couple's reunion comes after reports that Longoria's friend Kim Kardashian had begun dating Cruz.
However, the reality star has denied the rumours, posting on her Twitter that it is "not OK when magazines... involve [her] close friends in their made up stories".
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