Gillingham have signed Rotherham striker Delroy Facey, Barnet midfielder Barry Cogan and Swindon midfielder Aaron Brown on free transfers.
Brown, Cogan and Facey have all joined on free transfers
Facey, 27, scored 11 goals last season as Rotherham were relegated.
Cogan, 22, was released by Barnet despite being a regular last season while 27-year-old Brown helped Swindon win promotion from League Two.
They have also confirmed the signing of Cheltenham defender Craig Armstrong, 32, which was recently reported.
It has already been a busy summer of deals for Gills boss Ronnie Jepson.
Jepson has already signed Barnet defender Simon King for £200,000.
However, Matt Jarvis, Danny Jackman and Danny Spiller have left Priestfield to join Wolves, Northampton and Millwall respectively.
Defender Ian Cox has signed a new contract, while former striker Iffy Onuora has rejoined the club as first-team coach.