The PetSmart subsidiary's net loss was $82.9 million, or 21 cents a share, compared with a loss of $63.1 million, or 16 cents, in the year-earlier period.
The loss in the latest quarter included a non-cash share-based compensation charge of $43.8 million.
Sales were $1.15 billion, up 43% from $805.6 million a year earlier.
Analysts were expecting a loss of 11 cents and revenue of $1.13 billion, according to FactSet.
The adjusted loss before interest, taxes, depreciation and amortization was $29.2 million, narrowed from $53.4 million a year earlier.
Chewy shares fell 3.6% to $29.15 after hours. They closed the regular session down 18 cents at $30.25.
The company went public in June at an IPO price of $22 a share. The stock hit an intraday high of $41.34 on its first day of trading on June 14 and fell to $29.03 in July.
The company said it expected third-quarter sales to come in between $1.19 billion and $1.21 billion, a year-over-year increase of 36% to 38%. Analysts are expecting sales of $1.16 billion.