The Verizon iPhone 4 launched in February accounts for 32.3 percent of all iPhone 4s in the US market in July, according to mobile app analytics firm Localytics.
The only other iPhone carrier AT&T started to sell iPhone 4 last June or nearly eight months in advance.
The statistic shows that Verizon's iPhone 4 market shares increased from 20 percent in February to 26 percent in May, and jumped to a third by July.
Also, Verizon said it sold 2.2 million iPhones in first quarter compared to AT&T’s 3.6 million, including the cheaper $50 iPhone 3GS.
Market watchers suspect Verizon iPhone sales jumped this sharply at this time because Verizon's unlimited data plan is set to expire on July 7 and new data customers will have to choose one of its tiered plans.
Verizon Wireless will charge $30/month for 2GB data or $5 more a month than AT&T does and people wanted to grab the last opportunity of availing of the unlimited data plan.
Also another reason is that people whose AT&T contracts have expired, are migrating to verizon. AT&T has often been criticized for dropped calls and poor network service.
Verizon's network is considered by many to be better than AT&T's.
With rumors swirling about the iPhone 5 perhaps launching in September on multiple carriers, Verizon's recent market share gains may be a precursor of what is to come this fall, Localytics also added.