Dollar Tree was up about 12.8 percent, while Dollar General was up about 4.6 percent.
Dollar Tree reported earnings of 89 cents a share on revenue of $5.09 billion. Analysts had expected the company to post earnings of 81 cents a share on $5.10 billion in revenue, according to a consensus estimate from Thomson Reuters.
Dollar Tree also posted better-than-expected same-store-sales growth of 2.3 percent, compared to Wall Street estimates of 2.2 percent.
Dollar General reported earnings of $1.03 per share on $5.27 billion in revenue. Analysts had expected the company to post earnings of 95 cents a share on revenue of $5.28 billion, according to a consensus estimate from Thomson Reuters.
The company, however posted slightly disappointing same-store sales growth of 2.2 percent. Wall Street had expect comparable sales growth of 2.4 percent.
Shares of Dollar Tree and Dollar General are up 17 percent and 20 percent in the last year, respectively.