The dad of three only left jail in Spain in September last year after completing a 30-month prison sentence for a 2005 assault near Malaga.
Monday’s sentence followed his arrest over a May 2007 assault on three Spaniards at a brothel called Oxigeno, in Alhaurin el Grande, near Malaga.
The boxer’s two cousins Edward and David McGill were also arrested – but have yet to be located and tried.
The victims included brothel owner Francisco Gonzalez, who told three trial judges on September 26 that the boxer had punched his front tooth out as he tried to defend two customers Harrison and his cousins were attacking.
Lead judge Julian Cruz, in a sentencing document published on Monday, said: “Scott 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 criminal attack, in terms of where Francisco was hit, the serious injuries inflicted on the victims and the fact one of the accused was a professional boxer with extensive experience when it comes to fighting.”
Harrison was sentenced to two years in jail for the assault on Gonzalez and another two years for assaulting 39-year-old construction worker Salvador Jimenez, who was off work for 77 days with injuries to his knees, wrist and elbow.
Harrison was also fined £60 after being convicted of a third minor assault on Salvador’s pal Rafael Sainz, who committed suicide in January 2009.
Harrison was also ordered to pay nearly £8300 in compensation to his victims, including £1600 to the brothel owner for the loss of his tooth.
Harrison is expected to try to avoid starting his sentence immediately by launching an appeal against his conviction.
His defence lawyer Damian Canovas was unavailable for comment but has previously indicated he would appeal a guilty verdict and fresh prison sentence.
The boxer was thought to be preparing in Spain for this third fight since his comeback in June, although his exact whereabouts was unknown.
The Scot protested his innocence over the May 2007 bust-up during his one-day trial.
Gonzalez told the hearing the ex-world champ went for him as he tried to defend the other two Spaniards Harrison assaulted inside the sex club – allegedly with his two cousins – in an unprovoked attack.
The Scots trio are said to have laid in wait outside the club and attacked the the pair with their fists, feet, bottles and stones, as they left to find an ambulance.
Harrison, who attended court with his fiancee Stacey Gardner and son Jack, four, insisted: “All I tried to do was escape when people I’ve never met before started throwing bottles at us for reasons I didn’t know.
“I’ve no idea how the men who claimed we attacked them suffered their injuries.”
The judges trying Harrison dismissed his claims in their sentencing document, describing Mr Gonzalez’s account of events as “totally sincere.”
Harrison is due to fight Greenock man John Simpson, 29, on December 1.