BRUSSELS—The European Union's antitrust watchdog will as soon as Tuesday hit Alphabet Inc.'s Google with a fine of more than €1 billion ($1.12 billion) and demand changes to the company's business practices, according to people familiar with the matter.

The European Commission, which has for roughly seven years been investigating Google GOOGL, -1.07% GOOG, -0.97%  for breaching the bloc's antitrust rules in various areas, is poised to announce as soon as Tuesday that Google has manipulated search results to favor its own comparison-shopping service. Other formal EU probes into Google's behaviors with its Android mobile-operating service and AdSense advertising service are continuing.

The antitrust penalty against Google is expected to surpass the EU's previous record fine imposed on a company for allegedly abusing its market position: €1.06 billion against Intel Corp. INTC, -0.12%   in 2009.

"We continue to engage constructively with the European Commission and we believe strongly that our innovations in online shopping have been good for shoppers, retailers and competition," said Google spokesman Al Verney.

The EU will also likely demand Google give rival comparison shopping services such as Foundem.co.uk and Kelkoo.com Ltd. equal treatment in its search results. Complainants in the case allege that Google both demotes competitors' offerings in search rankings and artificially inserts its own service in a box above all other search results, regardless of their relevance.