The former Hills star and fiancé Jay Cutler welcomed baby boy Camden Jack earlier this month.
Taking to her Twitter page, Cavallari raved about her son, writing: "Being a mum is the most incredible feeling. I am so in love with this little boy!"
Cavallari announced her pregnancy in January, with Cutler's Chicago Bears teammate Earl Bennett revealing that the child would be a boy four months later.
In May, she reunited with her former Hills co-stars for a baby shower in Los Angeles.
Cavallari and Cutler got engaged for the second time in November 2011.