The company saw $874 million wiped off its shares after it shared its first guidance to expected earnings along with its new acquisitions, NextGen Networks, M2 Group and Amcom.
Vocus predicted $1.9 billion of revenue in 2016-17 with underlying earnings before interest, tax, depreciation and amortisation being between $430 million and $450 million.
Underlying net profit after tax was predicted at between $205 million and $215 million.
In the last 18 months, Vocus bought Amcom for $1.2 billion, M2 Group for $3.8 billion and Nextgen for $807 million.
Vocus chief executive Geoff Horth told shareholders at Tuesday's AGM that there would be an increase in second-half earnings.
The plunge in Vocus shares also affected TPG Telecom which lost seven percent of its share value to finish at $7.
Both companies have new competitors in the retail broadband market as the NBN rollout continues.
Competitors include Singapore's MyRepublic from Singapore, Vodafone, amaysim and Foxtel.
Last month, a failed plot to oust Horth led to Vocus shares taking a hit as well.