This investment targets both Acteco and Repsol's growth plan towards plastic waste management and recycling, Repsol said in a statement.
Acteco said the investment will double its plastic recycling capacity in the next five years.
Repsol said it is seeking to access quality plastic waste to create tools to develop new sustainable materials under its Reciclex range.
The group has pledged to recycle 20% of its production by 2030, and reach net zero emissions and carbon footprint by 2050.
"We are pleased to welcome Repsol as a partner and member of our management board," commented Juan Manuel Erum and Jorge Ramis, Acteco's founders.
"Repsol is a global multi-energy supplier that will contribute to develop our activity with new materials and markets. Repsol's investment in Acteco strengthens our position as a leader in the recycled plastic sector and the construction of a circular economy."
Acteco, which is based in Alicante, specialises in the collection, management, recycling and recovery of waste in Spain.
Repsol and Acteco have collaborated since 2018 to promote new circular economy models through the recovery and reincorporation of polymers in automobile, health, construction and packaging sectors.
The two firms collaboratively launched a project in 2020 to increase the capacity of Acteco's recycled material production plant in Ibi, Alicante.