The League One club terminated the contract of 38-year-old Barker on Wednesday, bringing to an end his 15-month spell in charge.
The announcement came less than 24 hours after the club's 0-0 draw against Swindon Town, which extended their winless league run to seven games.
That return has seen them slip to 12th in the table, with a statement on the club's official website reading: "Crawley Town Football Club can confirm that it has terminated the contract of first team manager Richie Barker with immediate effect.
"The club will make an announcement as soon as possible on who will look after team affairs in the interim period and we ask our supporters to have patience while the process of finding a new manager is undertaken.
"The club will not be making any further comment at this stage."
Barker took over the helm in August 2012, having led former club Bury to promotion from League Two during the 2010-11 campaign.
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