Harrison was found guilty of assaulting three men at a brothel following a trial in Malaga, receiving two years each for the two most serious attacks and a fine for the assault on the third victim.
The 35-year-old had returned to the ring in June with a stoppage victory in Glasgow over Hungarian teenager Gyorgy Mizsei Jnr after almost seven years away, and defeated Joe Elfidh on points at the city's Scottish Exhibition Centre in September.
Harrison's father Peter insisted his son is innocent and that he would fight the charges, saying: "Scott will be appealing this, 100 per cent.
"He has already said he is innocent and that remains the case. He’s down but determined to clear his name.
"Scott is a victim here – and I’m not just saying that because I’m his dad."
An attempt to appeal could allow Harrison to continue his comeback by fighting John Simpson, also in Glasgow, on December 1.
And he continues to set his sights on an all-Scottish world title fight with reigning WBO lightweight champion Ricky Burns, which promoter Frank Warren in September suggested could be a possibility if he continued to win.
But the Cambuslang resident now faces an uphill battle to prove his innocence and keep that goal alive, with the trial's lead judge Julian Cruz saying: "Harrison is not a first-time offender and his criminal record reflects a prior assault conviction.
"We’re also taking into account the dangerous nature of this attack, the serious injuries inflicted and the fact one of the accused was a professional boxer with extensive experience in fighting."
A Spanish legal source added: "For the appeal to be successful, Harrison will have to show the other witnesses, or victims, lied. Because there is an appeal, everything will be frozen until the appeal is heard."