Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a non-native and damaging pest of soybean [Glycine max (L.) Merr.] in the north central United States. We screened 78 soybean lines (maturity groups 000 to I) for resistance to soybean aphid and categorized resistance (i.e., antibiosis or antixenosis) in lines that showed putative resistance. Selected lines were also included in field trials at Rosemount and St. Paul, MN, in 2014. We detected antibiosis in PI 639534A, PI 639537, and PI 605765B and antixenosis in PI 507713. PI 605765B and PI 639537 performed better than susceptible varieties in both field trials with natural infestations of soybean aphid. We also documented antixenosis within IA3027, a line previously assumed to be susceptible to soybean aphid, which underscores the importance of including multiple susceptible and resistant controls for comparison in resistance screening studies. These additional sources of resistance may provide soybean breeders more options for incorporating resistance into early-maturing soybean varieties and allow different types of host plant resistance to be pyramided into varieties for growers.