The Serie A outfit confirmed the former Bologna boss as their new coach on Thursday after Edy Reja announced his resignation earlier in the day.
And Pioli has now revealed he turned down a two-year deal in favour of a contract that rewards him for European qualification.
"My staff and I will put all that we can into this to ensure that next season is a positive one," he said. "The club had offered me a two-year contract, but I have signed a one-year contract that is automatically renewable if we reach the objective of European football.
"I have come to Lazio to work, to achieve the objectives and to have an important season with results. They have always made me feel like first choice, we are focused on doing the best that we can.
"I like to have a direct approach, do everything and oversee everything, and those who will play on the Sunday will do so for how they train during the week.
"We want to be an aggressive team, playing a proactive football and to do that we have to work hard during the week."
Club president Claudio Lotito added: "The purpose of our choice was to find a person who had high technical and moral qualities and the right enthusiasm to trigger a process of substantial change within the system."
