The Portuguese giants dominated much of the encounter, with Rafa Silva, Gianluca Prestianni and Georgiy Sudakov finding the net to secure another three points for head coach Marco Silva's side.
Benfica took an early lead in the sixth minute when Rafa Silva bundled the ball into the net after Andreas Schjelderup's dangerous delivery caused confusion in the Lech Poznan defence.
The hosts continued to create opportunities but were unable to extend their advantage before half-time, despite coming close through Schjelderup, whose effort struck the crossbar in stoppage time.
Lech Poznan offered greater resistance after the break, but Benfica eventually doubled their lead in the 67th minute.
Gianluca Prestianni produced an impressive individual effort, beating his marker inside the penalty area before firing into the far corner to make it 2-0.
However, the visitors found a way back into the contest six minutes later when Leo Bengtsson capitalised on a costly defensive mistake by Benfica midfielder Enzo Barrenechea to score into an unguarded net.
The goal gave Lech renewed hope, but Benfica remained dangerous going forward and continued searching for a third.
Their efforts were rewarded in the 90th minute when Georgiy Sudakov finished confidently after receiving a pass from Barrenechea, restoring Benfica's two-goal advantage and confirming the victory.
Benfica maintain perfect Europa League record
The victory gave Benfica four wins from four matches in the Europa League league phase, strengthening their position among the leading teams in the competition.
The Portuguese side have also extended their winning run in all competitions to seven matches, demonstrating their growing confidence under Marco Silva.
Lech Poznan, meanwhile, remain without a victory in their recent European campaign, with the defeat extending their winless run to six matches.
Georgiy Sudakov was named Flashscore's Man of the Match following his influential performance, while Prestianni also impressed with his individual goal.
Benfica will now look to maintain their momentum as they continue their push for a place in the knockout stages.
Full-time: Benfica 3-1 Lech Poznan
Goalscorers:
• Benfica: Rafa Silva 6', Gianluca Prestianni 67', Georgiy Sudakov 90'
• Lech Poznan: Leo Bengtsson 73'