A modular transaction card assembly includes a card frame having the traditional dimensions of a credit card, and a transaction card that is smaller than a traditional card and that fits into a receptacle of the card frame. Each of the card frame and the transaction card may be capable of performing contactless data transactions individually. The combined assembly of the card frame with the transaction card secured in the receptacle is also capable of performing contact data transactions. The transaction card and/or the card frame may include one or more visual or tactile regions that allow the transaction card and card frame to be distinguished from other cards and/or to be properly oriented and aligned with one another when combined to form the card assembly.