Teresa Kidd, 44, admitted stealing the cash from Glasgow-based Maclay Murray and Spens LLP, where she worked as a purchase ledger supervisor.
Glasgow Sheriff Court heard how she duped bosses into signing documents that paid money into bank accounts owned by her and her then partner.
Sentence on Kidd was deferred and she was remanded in custody.
Sheriff John McCormick told her: "This was a complex fraud perpetrated repeatedly by a trusted employee at a firm of solicitors in Glasgow over a period of some five years."
He also told her: "A custodial sentence is almost inevitable."
Kidd, a grandmother, from Cumbernauld in North Lanarkshire, admitted embezzling the cash between October 2006 and November 2011.
The court heard how she joined the lawyers firm in 1987 where she "became a trusted member of staff" and was promoted to purchase ledger supervisor.
Procurator fiscal depute Lesley Chambers told the court: "As such she was responsible for making payments to creditors, clients and other beneficiaries using money withdrawn from the corporate bank account of Maclay Murray and Spens."
The court was told Kidd was in charge of staff within the purchase ledger team.
Mrs Chambers said that cash paid out would be drawn up on a "purchase run document" with a list of creditors, the amounts paid and the relevant bank details.
This was signed off by the financial controller who carried out random sample checks on outgoing payments.
A senior member of staff would check that the amounts tallied up with the outgoing details.
The court was told: "Faculty services limited regularly provide the service of advocates to Maclay Murray and Spens and as such they would subsequently submit invoices to them.
"The invoices to them were typically for a four-figure sum although in this particular case sometimes they rose to £10,000 and £11,000."
Mrs Chambers said that for some reason, unlike most invoices, those submitted by the faculty services did not include their bank details and employees had to manually input the details.
Kidd "exploited this" and only targeted invoices relating to the faculty services to carry out her crime.
She "double submitted" invoices to the law firm, one with the correct bank details so the cash was paid to faculty services, and a second invoice with her personal bank details.
Mrs Chambers added: "This practise of double submitting came to light on January 12, 2012."
An investigation into the matter was carried out and Kidd accepted full responsibility for what she had done.
A financial worker is facing a jail term for embezzling £176,696 from one of Scotland's top legal firms.