Leidos — May 5, 2026 release

Through ISS2, Leidos will support an enterprise environment serving approximately 5,900 federal and contractor end users and help sustain the resilient infrastructure, end-user services, and software ecosystem that underpin the SEC's mission to protect investors, maintain fair, orderly, and efficient markets, and facilitate capital formation. Leidos Holdings, Inc. Exhibit 99.1 2 FORWARD GUIDANCE Leidos is raising its fiscal year 2026 guidance as follows: FY26 Guidance Measure Current Prior Revenues (B) $18.00 - $18.40 $17.50 - $17.90 Adjusted EBITDA Margin Mid 13% Mid 13% Non-GAAP Diluted EPS $12.10 - $12.50 $12.05 - $12.45 Cash Flows Provided by Operating Activities (B) Approximately $1.80 Approximately $1.75 For information regarding adjusted EBITDA margin and non-GAAP diluted EPS, see the related explanations and reconciliations to GAAP measures included elsewhere in this release. Leidos does not provide a reconciliation of forward-looking adjusted EBITDA margins or non-GAAP diluted EPS to net income margin or diluted EPS due to the inherent difficulty in forecasting and quantifying certain amounts that are necessary for such reconciliation. Because certain deductions for non-GAAP exclusions used to calculate projected net income margin or diluted EPS may vary significantly based on actual events, Leidos is not able to forecast on a GAAP basis with reasonable certainty all deductions needed in order to provide a GAAP calculation of projected net income at this time. The amounts of these deductions may be material and, therefore, could result in projected net income margin and diluted EPS being materially less than what may be implied by projected adjusted EBITDA margins and non-GAAP diluted