The Croatian has been linked with a move to Juventus next season, should Lewandowski's arrival from Borussia Dortmund be confirmed as expected.
However, his representative Ivan Cvjetkovic sees no reason why Mandzukic would want to leave the current European and world champions.
"Mandzukic is focusing on Bayern Munich and after the end of this season, he still has two years on his contract and he is happy in Munich," Cvjetkovic told Italy's Tuttosport newspaper.
"(Bayern coach Pep) Guardiola rates Mandzukic a lot and he's shown that over the first half of the season.
"Mandzukic wants to defend the Champions League title."
The 27-year-old is Bayern's top goalscorer this season with 10 goals and he has held down a regular place in the team, in spite of Guardiola's penchant for a strikerless team.
However, with Guardiola rarely playing two forwards, the possible arrival of Lewandowski in the summer could lead to either Mandzukic of Claudio Pizarro seeking a move away given the potential lack of action next season.