Alexander Garfin had someone to share his experiences with as he embarked on his professional acting career before he had even entered kindergarten: his brother, Maximilian Garfin, was also a young, aspiring actor, and the two pursued their careers as child performers concurrently. The first break for the Manhattan-born Garfin came at the age of three, when he appeared in a number of video releases for the kids network Nickelodeon. By five, he was playing a very young Russian spy in training in the Angelina Jolie movie "Salt" (2010) for which the five-year-old actor had his hair and eyebrows dyed blonde. In 2013, at nine years old, Garfin made his first appearance on an Equity stage, appearing in a production of the Joel Grey play "On Borrowed Time" with the Two River Theater Company in Red Bank, NJ. He also booked a number of prominent commercials around this time. In 2014, it was announced that Garfin would be providing the voice of Linus for the big screen adaptation of the comic strip "Peanuts" (2015).