Weaver, who was named EV-P for PR and brand management, was previously V-P of IR at AT&T, and had been working closely with Martin in what she concedes was an informal succession plan.
She will oversee a comms staff of nearly 200 people. AT&T is in the process of searching for a new IR head. Weaver will report to CEO C Michael Armstrong and CEO-elect David Dorman, who is expected to assume Armstrong's role later this year.
Weaver said the increasingly close co-operation between the IR and PR functions should ease her transition.
'It's hard to do IR and not be married to your PR people these days,' said Weaver.
'It's allowed Dick and I to work very closely during our six years together,' she added.
Previously, Weaver worked within the IR departments of Microsoft and MCI Communications.
She takes the comms helm at a time of transition for both AT&T and the telecoms industry in general. The firm is in the process of divesting itself of the cable assets it bought during the boom-time 1990s, while much of the rest of the industry is hit by scandals and mountains of debt.
Weaver said she believes that AT&T will emerge from its forthcoming cable divestiture with a more streamlined operation and more straightforward comms.
She also hinted that the firm was in a good position to attract customers from some of its embattled competitors: 'We are going to be running a focused communications firm. One that knows who its customers are and what its business model is.'