Lawmakers spent hours discussing the plan, wrapping up late Sunday night.
The bill now heads to the Illinois House, which could take up the matter after the Memorial Day holiday.
One of the main challenges for Democrats was Governor Pritzker's request for $800 million in new tax revenue.
The money would come from extra revenues on items like an increased sports wagering tax and a cap on corporate tax deductions.
Earlier this month, the governor's office warned the leaders of agencies across the state to prepare for cut-backs if lawmakers don't pass the budget.