A series of 2-amino-4,5,6,7-tetrahydrothieno[2,3-c]pyridines were prepared and evaluated as potential allosteric modulators at the A1 adenosine receptor. The structure–activity relationships of the 3- and 6-positions of a series of 2-amino-4,5,6,7-tetrahydrothieno[2,3-c]pyridines were explored. Despite finding that 3- and 6-substituted 2-amino-4,5,6,7-tetrahydrothieno[2,3-c]pyridines possess the ability to recognize an allosteric site on the agonist-occupied A1AR at relatively high concentrations, the structural modifications we have performed on this scaffold favor the expression of orthosteric antagonist properties over allosteric properties. This research has identified 2-amino-4,5,6,7-tetrahydrothieno[2,3-c]pyridines as novel class of orthosteric antagonist of the A1AR and highlighted the close relationship between structural elements governing allosteric modulation and orthosteric antagonism of agonist function at the A1AR.