The comScore survey covering the three months ending in January showed Apple grabbed 37.8 percent of the smartphone market, an increase of 3.5 percentage points from the prior three-month period.
Samsung also boosted its market share, but at a slower pace. The South Korean electronics giant held 21.4 percent of the US smartphone market, up from 19.5 percent previously, comScore said.
The two leaders were well ahead of other rivals, including Taiwan's HTC, in third pace with 9.7 percent, Motorola (8.6 percent) and South Korean LG (7.0 percent.
The data showed Apple, which has been losing ground globally to the Google Android system, reversed some of that trend in the US market during the period.
Android's share slipped 1.3 points to 52.3 percent, while Apple's iOS gained 3.5 points to 37.8 percent, comScore said.
BlackBerry's platform fell to 5.9 percent from 7.8 percent and Microsoft's Windows Phone slipped a fraction to 3.1 percent.
Apple introduced its iPhone 5 in the United States in September, and also saw strong demand for its earlier versions that were discounted following the launch.
Microsoft released its Windows Phone 8 operating system in late October.
The comScore survey found 129.4 million people in the US owned smartphones in the period, a seven percent increase from October.