
Immobile struck with a spectacular volley from a corner in the 26th minute and put them back in front with a deflected shot before halftime after Mirco Antenucci had briefly put SPAL on level terms.
Lazio, thumped 3-0 by Inter on Monday, completed their win at a soggy Stadio Olimpico with long-range efforts from Danilo Cataldi and Marco Parolo in the second half.
The match pitted Lazio midfielder Sergej Milinković-Savić against his younger brother Vanja, who was playing in goal for SPAL.
Lazio’s seventh win in 11 games this season moved them up to fourth in the table with 21 points while SPAL dropped to 15th on 12. Neither team has drawn a game.