Ruth Munro's mother, Margaret McPartlin, died in September 1993 aged 73.
But a court heard she continued to draw Ms McPartlin's pensions from British Steel Corporation and Diageo.
Munro, 67, from Tullibody, Clackmannanshire, admitted defrauding the schemes of Â£18,577.
Alloa Sheriff Court was told that between 1993 and May 2015 - by which time Ms McPartlin would have been 94 - she pretended to the administrators of both pension schemes that her mother was still alive.
Sheriff Linda Smith deferred sentence for a criminal justice social work report until 10 November and ordered Munro to reappear then.
She said: "I'll continue this for reports to be made available."
It is expected that Munro's solicitor, Jay Goodwillie, will outline mitigating circumstances at the November hearing.

Some 789 people at a music festival in eastern Finland went skinny dipping on Saturday, organisers said, beating the previous record set in Australia by just three, reports said.
Organisers were waiting for Guinness World Records to confirm the record.
It is the third Finnish attempt at the record, Yle news website said.
Previous attempts in Helsinki in 2015 and 2016 each attracted about 300 participants.
Organisers at the Ilosaari Rock music festival in Joensuu had hoped to entice 1,000 people into the chilly water.
As in previous attempts, only a few hundred volunteers appeared to be willing to participate, but shortly before the event was due to begin the sun came out and this boosted the numbers, Yle reported.
The record they were hoping to break was achieved in 2015 in Perth by 786 people at an attempt to celebrate positive body image.
Outdoor swimming is a tradition in Finland, where "avantouinti" - ice-hole swimming - is promoted by the country's tourist board as an energy-boosting experience.

The Spanish had lost the last three finals and holders France moved in front with a Mathilde Bourdieu tap-in.
Patricia Guijarro fired home to level but a curled finish from Emelyne Laurent restored France's lead.
Damaris Egurrola made it 2-2 and France's Pauline Dechilly was sent off before Guijarro headed in the winner.
It was a repeat of last year's final but this time Spain emerged victors after losing in the final four times in the last five years.
Bourdieu slotted in from Laurent's cross in the fourth minute at Windsor Park to give France the perfect start.
Guijarro stretched to finish from a corner 14 minutes later but France were back in front when Laurent raced clear and curled beyond keeper Noelia Ramos with 19 minutes left.
Egurrola met Carmen Menayo's free-kick to head in on 85 minutes and Dechilly was dismissed for two yellow cards two minutes later.
The last-minute winner came from another Menayo free-kick, this time with Guijarro connecting at the back post to complete her double and clinch a thrilling victory.
A woman has admitted pretending her dead mother was still alive for more than 20 years so she could carry on drawing her pension.
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Hundreds of naked swimmers have taken to the water in Finland in a bid to break the world record for the biggest naked swim.
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Spain scored twice in the last five minutes to beat France 3-2 in a dramatic Women's European U19 Championship decider in Belfast.