We have measured the weak radiative decay branching ratio (∑+ →pγ)/(∑+ →pπ0). The experiment was carried out at Brookhaven National Laboratory using a low-energy separatedK− beam stopping in liquid hydrogen. The∑+ was tagged by observing the pion fromK−K+p→∑+π− in a range telescope, and the gamma was detected in a segmented NaI detector. The result is (2.81±0.39−0.43+0.21)×10−3, which is consistent with previous measurements. This corresponds to a branching ratio for (∑+ →pγ)/(∑+ → all) of (1.45±0.20−0.22+0.11)×10−3, where the quoted errors are statistical and systematic, respectively. A total of 408 signal events were observed, doubling the previous world total.