The 30m was planted in the grounds of Wrest Park near Silsoe, Bedfordshire, in 1856 by Thomas de Grey.
It was brought into the mansion for the family's Christmas celebrations and re-planted once the festivities were over.
This year English Heritage, which runs the estate, has used a cherry picker to put a 3ft star at the top and visitors can now decorate the lower branches with ribbons.
From the mid-19th Century, gardeners would bring trees in from the garden during the festive period so families could adorn them with candles, sweets and homemade decorations.
English Heritage said it recently discovered reference to the Wellingtonia’s use as a Christmas tree in the Gardener’s Chronicle, which became Horticulture Week in the 1960s.
The article stated: "It is said to have been planted by the late Mr Snow in 1856, and must therefore have been one of the first introduced into this country."
"Mr Ford, the late gardener at Wrest Park ... has carried the plant many times from the conservatory to the mansion, and vice versa."
English Heritage’s head of gardens and landscape John Watkins said the Wrest Park team were delighted to restore the festive tradition.
"The Christmas tree at Wrest Park is a rare, documented example of a tree that was decorated and replanted annually during the Victorian period.
"It was planted shortly after the trend for Christmas trees began and we believe it is one of the earliest examples. If anyone knows of an earlier one, we’d like to hear about it."
Christmas trees became fashionable by the 1850’s after being adopted by the royal family as part of their celebrations.