Timothy, 26, who has played in the top-rated Vietnamese football championship league for five years, is the first foreign player signed by the Central Highland team in preparation for the new football season.
Sources say the Nigerian striker will start playing for Hoang Anh Gia Lai at a salary of US$4,000 per month, lower than the amount he was paid by his previous team.
The contract with the Nigerian striker will fill the vacancy created by Nigerian Oseni Bolaji, who left the team after his one-year contract ended, and improve the team's offensive skills.
The Gia Lai team have not won a V-League trophy since 2005, after grabbing the title in 2003 and 2004.
Timothy debuted in the V-League when he played for Dong Thap in 2009, before joining and playing for Hoa Phat Hanoi during 2009-11.
He scored 17 goals to emerge as the V-League's top scorer in 2011 before joining Vietnamese striker Le Cong Vinh to play for the Hanoi Football Club in 2012.
He then signed a one-year contract with Ninh Binh in 2013.
Hoang Anh Gia Lai established the first international-standard football training centre in Vietnam, the Hoang Anh-Gia Lai-JMG-Arsenal Football Academy, in co-operation with Arsenal in 2007, with an investment of US$4 million in Gia Lai.