Al Hasawi met with manager Alex McLeish on Tuesday before the Scot left the club by mutual consent, bringing an end to his 40-day reign.
The former Birmingham boss was reportedly unhappy with Forest's January transfer dealings and agreed to part company with Al Hasawi having only taken the position on 27 December following the departure of Sean O'Driscoll.
"The challenge is bigger than I envisaged when we purchased the club but I will do everything I can to bring success back to the followers of Forest," Al Hasawi said.
"I cannot pretend the last six months or so have been an easy time, either for myself and my family or the club as a whole.
"I know many of our fans are frustrated. I want them to know I share their frustrations but I remain as committed as ever.
"We have a strong vision and plan for Nottingham Forest and our willingness to succeed remains undimmed by the disappointments we have experienced in the past six months - we will return Nottingham Forest to its former glory."