The Cardenales de Lara team posted about the deaths at 12:38 a.m., describing the traffic accident as "a terrible tragedy".
The two were teammates for Lara, which played at Caracas on Thursday night.
According to media accounts from Venezuela, the crash occurred in Yaracuy.
Valbuena, an 11-year major league veteran, hit.199 with nine homers and 33 RBIs in 96 games this year for the Los Angeles Angels, who released him on August 7.
"We are saddened by the tragic news that Luis Valbuena and former major leaguer Jose Castillo have died in a auto accident", the organization tweeted. "Our thoughts and prayers are with their loved ones during this time of grief", the Angels said in a tweet.
Valbuena turned 33 on November 30.
Castillo played from 2004 to 2008 in the majors with the Pittsburgh Pirates, San Francisco Giants and Astros. His best year came in 2016 when he batted.260 and slugged.459 while hitting 13 home runs and collecting 40 RBI for the Houston Astros.
He played mostly second base and third base. He had four hits in seven at-bats with a walk during the late-August/early September appearances.