Esat Telecom applied a number of times for a telecommunications licence to the Department of Communications and was finally granted a limited one in March 1993.

It was the first domestic competitor to Bord Telecom Éireann (now Eircom) and, after initially reselling leased lines from that company, used "autodiallers" to route calls onto its network.

These devices proved controversial, with Telecom Éireann threatening legal action and the Department of Communications contending that these were a breach of Esat's limited licence.

In 1996, Esat Telecom, in conjunction with Telenor AB, bid successfully for the second GSM mobile telecommunications licence, against five other consortia.

The Moriarty Tribunal found in 2008 that the awarding of the licence was influenced by payments made by O'Brien to Michael Lowry, the Minister for Transport, Energy and Communications.

Also in 1999, Esat bid for Cablelink Limited, the cable and television company owned jointly by Telecom Éireann and RTÉ.

In 1999, Esat Telecom was the first wholly owned Irish company to lay two optical submarine cables between Ireland and the UK.

Esat for its part retaliated by threatening to sue Telenor, and making repeated offers to buy the Norwegian company out.

Eventually, in November 1999, Telenor bid for the entire share capital of Esat Telecom Group plc as a way of solving the situation.