Online betting figures for 2017 show gross gaming revenue for sports and casino games rocketed to €560 million ($687 million), driven largely by sports.
Christian Tirabassi, senior partner at consultancy firm Ficom Leisure, said Spain is "on the radar of the international market".
"I definitely see the market growing both in online and retail betting and think this market will easily hit €1 billion to €1.5 billion in the next three to five years," added Tirabassi, speaking at a betting on football
conference in London.
Tirabassi said the Spanish betting market was maturing and had grown considerably over the past three decades. The first betting shop did not open until 2008.
Jacob Lopez Curciel, chief executive of sports betting and gaming company Optima, said there were still opportunities in Spain, unlike in other countries where the market was "saturated".
But he warned that too much in the way of new regulations could make it too expensive for betting operators to enter the market.
"There could be some consolidation such as multimedia products and between retail and online," he said, adding that horse racing could add more choice for Spanish punters.
"The operators and suppliers of technology for racing are producing streaming and will work very well for Spanish players," he said.
"At the moment for Spanish players the sports they bet on are football, basketball and tennis but I think horse racing is growing, quite fast actually, and it is a product that has to be there."
Mikel Lopez de Torre, chairman of Spanish online gambling trade body Jdigital, said consolidation was inevitable, given it has already begun in Britain.
He agrees the billion-euro mark will be reached but believes there will be changes in the market as it matures.
"I think there is certainly going to be consolidation," he said.
"There are 50 brands (bookmakers) and another 10 or 12 in the pipeline and there is already consolidation happening in the United Kingdom, which will impact.
"It is hard to see how we can make room for 12 more brands without seeing any consolidation beginning with those at the bottom of the pyramid and that has to start in the next five years."
By Pirate Irwin / AFP