Italy's paramilitary Carabinieri police and anti-terrorism officers in the Piedmont capital Turin arrested 35-year-old Nicola Gai and Alfredo Cospito, 46 at their apartment in the city.
Police said Cospito's girlfriend was also under investigation for the 7 May kneecapping of Adinolfi by two masked gunmen aboard a motorbike as he left his home in a leafy suburb of Genoa to go to work.
"They acted alone," said Genoa's prosecutor Michele Di Lecce, who said the pair were arrested after investigators listening in on phone conversations feared they could flee the country.
"They face charges of grievous bodily harm, carrying illegal weapons and the theft of the motorcycle used to carry out the attack."
Gai and Cospito were arrested based on evidence from surveillance cameras , from wiretaps and from analysis of a hand-written leaflet claiming responsibility for the attack.
Italy's interior minister Annamaria Cancellieri praised police for "a high-level success following a complex investigation" and premier Mario Monti also congratulated police in a statement.
The previously unknown 'Olga' cell of the Greek-linked Informal Anarchist Federation (FAI) claimed Adinolfi's shooting in a leaflet mailed to Italian daily Corriere della Sera in an envelope bearing a Genoa postmark.
The leafllet urged further attacks and called Adolfini a "grey assassin", blaming him and and the former conservative Italian government for trying to reintroduce nuclear power in Italy.
It railed against Ansaldo and a long list of Italian state companies, as well as the European and global nuclear industry."
Adolfini was hospitalised and had to undergo surgery to his leg after the attack.
The FAI claimed responsibility for a package bomb found outside the Greek embassy and defused in December 2010. Nobody was injured in the incident, but two parcel bombs at the Chilean and Swiss embassies in the Italian capital on that same month seriously injured two people who opened them.