Exhibit 99.1

Calgary, April 28, 2011

Imperial Oil announces estimated first-quarter financial and operating results

Bruce March, chairman, president and chief executive officer of Imperial Oil, commented:

“Imperial Oil delivered a first quarter of solid results with earnings of $781 million or $0.91 per share, up from $476 million in the first quarter of 2010. The 64 percent earnings increase resulted from improved industry refining margins, higher Syncrude and Cold Lake production and lower refinery planned maintenance activities. These factors were partially offset by the unfavourable foreign exchange effects of the stronger Canadian dollar. Reliability and expense management improvements in all operating segments allowed us to capture higher crude oil realizations in the Upstream and improved margins in petroleum product markets.

Our long-term business approach continues to support robust activity and exceptional growth, while achieving operational excellence in our base business. Capital and exploration expenditures were $859 million in the first quarter, funded from cash flow generated from operations. Our ability to deliver on the elements we can control, while meeting our objective of continuous improvement will continue to reward our shareholders in the future.”

Imperial Oil is one of Canada’s largest corporations and a leading member of the country’s petroleum industry. The company is a major producer of crude oil and natural gas, Canada’s largest petroleum refiner, a key petrochemical producer and a leading marketer with a coast-to-coast supply network that includes about 1,850 retail service stations.

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First quarter items of interest

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First quarter 2011 vs. first quarter 2010

The company’s net income for the first quarter of 2011 was $781 million or $0.91 a share on a diluted basis, compared with $476 million or $0.56 a share for the same period last year.

Earnings in the first quarter were higher than the same quarter in 2010 primarily due to stronger industry refining margins of about $175 million, higher Syncrude and Cold Lake volumes of about $100 million and lower refinery planned maintenance activities of about $85 million. These factors were partially offset by the unfavourable foreign exchange effects of the stronger Canadian dollar of about $70 million. Reliability and expense management improvements in all operating segments allowed the capture of higher crude oil realizations in the Upstream and improved margins in petroleum product markets.

Upstream net income in the first quarter was $528 million, $84 million higher than the same period of 2010. Earnings increased primarily due to higher volumes and lower maintenance costs at Syncrude totaling about $80 million. Earnings were also positively impacted by higher Cold Lake bitumen production of about $30 million and higher crude oil commodity prices of about $30 million. These factors were partially offset by the unfavourable foreign exchange effects of the stronger Canadian dollar of about $50 million.

The average price of Brent crude oil in U.S. dollars, a common benchmark for world oil markets, was $105.01 a barrel in the first quarter of 2011, up almost 40 percent from the corresponding period last year. The company’s average realizations on sales of Canadian conventional crude oil and synthetic crude oil from Syncrude production also increased. The company’s average bitumen realizations in the first quarter were about ten percent lower than that in the first quarter of 2010, reflecting a widened price spread between the lighter crude oils and Cold Lake bitumen, primarily due to continuing impacts from third party pipeline integrity issues on heavy oil markets.

Gross production of Cold Lake bitumen averaged 157 thousand barrels a day during the first quarter, up from 148 thousand barrels in the same quarter last year. Higher volumes were the result of the ongoing development drilling program partially offset by the cyclic nature of production at Cold Lake.

The company’s share of Syncrude’s gross production in the first quarter was 80 thousand barrels a day, versus 67 thousand barrels in the first quarter of 2010. Increased production was primarily the result of improved mining and upgrading reliability as well as lower planned maintenance activities.

Gross production of conventional crude oil averaged 22 thousand barrels a day in the first quarter, down from 24 thousand barrels the same period last year, due to natural reservoir decline.

Gross production of natural gas during the first quarter of 2011 was 269 million cubic feet a day, down from 273 million cubic feet in the same period last year. The lower production volume was a result of natural reservoir decline.

Net income from Downstream was $276 million in the first quarter of 2011, $237 million higher than the same period a year ago. Earnings benefited from stronger industry refining margins of about $175 million due in part to favourably priced crude mix processed and improved demand for petroleum products, as well as the favourable impact of about $85 million associated with lower planned refinery maintenance activities. These factors were partially offset by the unfavourable effects of the stronger Canadian dollar of about $20 million.

Chemical net income was $38 million in the first quarter, $39 million higher than the same quarter last year. Improved industry margins across all product channels, lower costs due to lower planned maintenance activities, and higher polyethylene sales volumes were the main contributors to the increase.

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First quarter 2011 vs. first quarter 2010 (continued)

Net income effects from Corporate and other were negative $61 million in the first quarter, compared with negative $6 million in the same period of 2010. Unfavourable earnings effects in the first quarter were primarily due to changes in share-based compensation charges.

In the first quarter, cash flow generated from operating activities was $959 million, and $822 million was invested in additions to property, plant and equipment, mostly associated with the Kearl oil sands and other growth projects. The company’s balance of cash was $301 million at March 31, 2011, compared with $267 million at the end of 2010.

Key financial and operating data follow.

Forward-Looking Statements

Statements in this report relating to future plans, projections, events or conditions are forward-looking statements. Actual future results, including project plans, costs, timing and capacities; financing sources; the resolution of contingencies and uncertain tax positions; the effect of changes in prices and other market conditions; and environmental and capital expenditures could differ materially depending on a number of factors, such as the outcome of commercial negotiations; changes in the supply of and demand for crude oil, natural gas, and petroleum and petrochemical products; political or regulatory events; and other factors discussed in Item 1A of the company’s 2010 Form 10K.

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Attachment I

IMPERIAL OIL LIMITED

FIRST QUARTER 2011

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Attachment II

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FIRST QUARTER 2011

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Attachment III

IMPERIAL OIL LIMITED

FIRST QUARTER 2011

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Attachment IV

IMPERIAL OIL LIMITED

FIRST QUARTER 2011

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Attachment V

IMPERIAL OIL LIMITED

FIRST QUARTER 2011

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