SEC FORM 13F-HR

The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F COVER PAGE

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Report for the Calendar Year or Quarter Ended: 06-30-2015
Check here if Amendment    Amendment Number:
This Amendment (Check only one.):    is a restatement.
   adds new holdings entries.
Institutional Investment Manager Filing this Report:
Name: SEI Investments Co
Address: 1 Freedom Valley Drive
Oaks, PA  19456-1100
Form 13F File Number: 028-16454
CRD Number (if applicable):
SEC File Number (if applicable):

The institutional investment manager filing this report and the person by whom it is signed hereby represent that the person signing the report is authorized to submit it, that all information contained herein is true, correct and complete, and that it is understood that all required items, statements, schedules, lists, and tables, are considered integral parts of this form.

Person Signing this Report on Behalf of Reporting Manager:
Name: N. Jeffrey Klauder
Title: Executive Vice President
Phone: 610-676-2701
Signature, Place, and Date of Signing:
N. Jeffrey Klauder OaksPA 08-03-2015
[Signature] [City, State] [Date]
SEI Investments Company (SEI) is the parent holding company of certain institutional investment managers, as defined by Section 13(f) of the Securities Exchange Act of 1934, as amended (the "Act"). For purposes of the reporting requirements under Section 13(f) of the Act, and the rules promulgated thereunder, SEI does not exercise, and therefore disclaims, investment discretion with respect to any Section 13(f) securities positions over which its investment operating subsidiaries exercise such discretion. To the extent, however, that SEI's ownership interest in such subsidiaries may nevertheless give rise to a Form 13F obligation for SEI, the information required by Form 13F is reported herein on behalf of the following subsidiaries: SEI Investments Management Corporation ("SIMC"), SEI Trust Company and SEI Investments Canada Company (SEI Canada). Voting authority with respect to the Section 13(f) securities reported herein resides with and is exercised by SEI's operating subsidiaries, unless otherwise indicated. Although SEI has not been delegated voting authority over such Section 13(f) securities, and disclaims such voting authority, pursuant to instruction 12b.viii of Form 13F, and for that purpose only, such Section 13(f) securities are reported as "Sole Voting Authority." SIMC and SEI Canada each serve as an investment adviser to a number of pooled investment vehicles, which may include mutual funds, hedge funds, private equity funds, collective investment trusts and offshore investment funds (together, the "Pooled Investment Vehicles"). In addition, SIMC sponsor and may serve as adviser to, separately managed account programs (SMA Programs) . SIMC and SEI Canada may act as a "manager of managers" whereby each retain, subject to SIMC's and SEI Canada's oversight, respectively, sub-advisers to buy and sell securities on behalf of such Pooled Investment Vehicles and SMA Programs. To the extent that SIMC's and SEI Canada's role as a manager of managers could give rise to a Form 13F obligation, SIMC or SEI Canada has instructed its sub-advisers to file a Form 13F with respect to such securities and has included such sub-advisers in the "list of other managers reporting for this manager" below.
Report Type (Check only one.):
   13F HOLDINGS REPORT. (Check here if all holdings of this reporting manager are reported in this report.)
   13F NOTICE. (Check here if no holdings reported are in this report, and all holdings are reported by other reporting manager(s).)
X 13F COMBINATION REPORT. (Check here if a portion of the holdings for this reporting manager are reported in this report and a portion are reported by other reporting manager(s).)
List of Other Managers Reporting for this Manager:
[If there are no entries in this list, omit this section.]
Name Form 13F File No. CRD No. (if applicable) SEC File No. (if applicable) CIK
1832 Asset Management L.P. 028-11685      
Acadian Asset Management LLC 028-05990      
AJO, LP 028-05508      
AllianceBernstein L.P. 028-10562      
Analytic Investors, LLC 028-04895      
AQR Capital Management LLC 028-10120      
AJO, LP 028-05508      
Arrowpoint Asset Management LLC 028-13791      
Ashmore Equities Investment Management LLC 028-05804      
Beutel Goodman Capital Management 028-02951      
Brigade Capital Management, LP 028-12820      
Brown Advisory 028-05775      
CastleArk Management LLC 028-05573      
Causeway 028-11728      
Columbia Management Advisors LLC 028-00297      
Delaware Investments 028-13120      
Earnest Partners LLC 028-05269      
Fiduciary Management Associates 028-06071      
Fiera Capital Corp. 028-14036      
Guggenheim Capital Llc 028-12836      
Hexavest Inc. 028-12180      
Hillsdale Investment Management Inc. 028-11957      
Intech Investment Management LLC 028-04211      
Investec Asset Management Ltd. 028-12634      
Jackson Square Partners Ltd 028-16230      
Jennison Associates LLC 028-00074      
JP Morgan Investment Management 028-11937      
Kleinwort Benson Investors International LLC 028-13513      
Lazard Asset Management Ltd 028-10469      
Legal & General Investment Management America Inc 028-15066      
LMCG Investments, LLC 028-13608      
LSV Asset Management 028-06580      
Martingale Asset Management LP 028-04632      
Montibus Capital Management LLC 028-15069      
Montrusco Bolton Investments Inc. 028-13628      
Mt Lucas Management LP 028-11021      
Neuberger Berman Group LLC 028-13573      
OppenheimerFunds Inc. 028-00203      
PanAgora Asset Management Inc. 028-03042      
Parametric Portfolio Associates LLC 028-04558      
PCJ Investment Counsel Ltd 028-12690      
QS Investors LLC 028-14009      
Quantiative Management Associates 028-11173      
RWC Asset Management LLP 028-14481      
Security Capital Research & Management Inc 028-07312      
Snow Capital Management LP 028-10613      
Spectrum Asset Management, Inc. 028-11300      
State Street Global Advisors Capital Management Trust Company 028-12575      
State Street Bank & Trust 028-00733      
Stone Harbor Investment Partners LP 028-14178      
Tradewinds Global Investors, LLC 028-12572      
Waddell and Reed Financial Inc 028-07592      
WCM Investment Management/CA 028-07104      
Blair William & Co/IL 028-04871      
Form 13F Summary Page
Report Summary:
Number of Other Included Managers: 3
Form 13F Information Table Entry Total: 4,957
Form 13F Information Table Value Total: 11,061,281
(round to nearest dollar)
List of Other Included Managers:
Provide a numbered list of the name(s) and Form 13F file number(s) of all institutional investment managers with respect to which this report is filed, other than the manager filing this report.
[If there are no entries in this list, state “NONE” and omit the column headings and list entries.]
No. Name Form 13F File No. CRD No. (if applicable) SEC File No. (if applicable) CIK
1 SEI Investment Management Company 028-16475      
2 SEI Trust Company 028-10297      
3 SEI Investments Canada Company 028-16449