A court in the city of Valencia said it has concluded "there exists an employment relationship between the two parties" in the case of the rider who had worked for Deliveroo since October 2016 and was recently fired for "lack of availability".
The court ordered he be reinstated or be paid €705.13 ($821.97) in compensation, according to the ruling dated June 1st which was made public Monday.
Online food platforms have boomed worldwide, allowing people to order from local restaurants via mobile phones, with dishes delivered to their homes or offices shortly afterwards, often by young bicycle couriers.
Companies like Deliveroo and other gig economy groups such as Uber are involved in legal battles in several countries over whether drivers should be classified as employees, which makes the firms responsible for paying minimum wages and making social benefit contributions. In Spain, another case is being fought in the courts in Barcelona.
Deliveroo said it would study the Valencia court's ruling "before deciding its next steps".
"The case refers to a delivery man who had an older contract which does not reflect the existing method of cooperation between 'riders' and Deliveroo," it added in a statement.
Deliveroo said the "self-employed" status of riders in its new contracts had been "confirmed" by courts across Europe.
Local union Intersindical Valenciana, which had backed the rider in his court case, said the ruling was "very positive" and in line with a recent report by the Labour Inspectorate of Valencia calling for Deliveroo riders to be considered employees.