Cajuste spent much of deadline day at La Rosaleda finalising the paperwork before the club confirmed his arrival minutes before the market closed, with the 27-year-old already registered to play in LaLiga.
The move includes a purchase option in the region of eight million euros, giving newly promoted Málaga the chance to make the signing permanent next summer without any obligation to do so.
The Swedish international arrived in Málaga on Monday night, passed his medical on Tuesday and spent the afternoon at the club's stadium as the deal was finalised. He joins after two seasons on loan at Ipswich Town, spells that included promotion to the Premier League followed by an immediate return to the Championship, and brings previous experience at Napoli, Stade Reims and Midtjylland.
Cajuste has played in Serie A, the Premier League and Ligue 1, competed in the Champions League, and has been a full Sweden international since 2020.
Sporting director Loren Juarros identified central midfield as an area requiring physical reinforcement to complement the technical quality already present in Juanfran Funes's squad, and Cajuste's profile as a combative, ball-winning presence fills that specific need. His arrival completes a summer of eight signings at Martiricos, following Fernando Calero, Juan Cruz, Carlos Dotor, José Salinas, Pablo Martínez, Adam Aznou and Juan Berrocal through the doors as Málaga prepare for a return to the Spanish top flight.
The window's final day also brought one departure, with Pablo Arriaza renewing his contract until 2028 before immediately joining Segunda RFEF side Estepona on loan in search of regular first-team football under Manolo Sánchez, previously assistant to Sergio Pellicer at Málaga.
Málaga had not entirely ruled out further activity before the deadline and explored the possibility of an additional signing, but a lack of room to complete a corresponding departure left no space in the squad for a ninth arrival.
Cajuste therefore became the final piece of a summer rebuild that has touched almost every area of the squad, giving Juanfran Funes a markedly different profile of options in central midfield compared with the group that secured promotion last season.