The 40-year-old had been available for a short period of time following his release by Fulham at the start of the month.
Having committed his future to Stamford Bridge for the next 12 months, the Australian international described his new employers as a "phenomenal club".
"It's a phenomenal club. It's one of the biggest and best clubs in the world, and it's an honour to sign for Chelsea. I didn't take much convincing to come here," he told the club's official website.
Schwarzer arrived on English shores back in 1997 with Middlesbrough and spent 11 years at the Riverside, before having five seasons with Fulham.