She also shared a before snap from the salon that appears to have been taken just minutes prior to the drastic cut.
The blunt bob is a trendy style that many celebrities have taken a liking to as of late, including Khloe Kardashian, who showed off a longer variation of the 'do -- the "lob" -- in October at her sister Kim Kardashian's baby shower.
In addition to her fierce new hairstyle, Hilary was also kind enough to share an adorable snap of her 3-year-old son, Luca. "About to kiss this face right off," the proud mama captioned the shot.
This isn't the first time, Hilary has gushed about her little man, either.
"I feel really lucky just to watch him every day grow and become a little person with his own opinions and his own ideas," the "Sparks" singer told ET in June. "It's really beautiful to watch. He's the sweetest little spirit and we have so much fun. In bed at night, reading books, all the simple things are really the ones I cherish the most. He's so funny right now too ... it's a great age."
For more about how Hilary feels being a mom and her relationship status with her ex, Mike Comrie, watch the video below.