Exhibit (a)(xxvi)

WILLIAM BLAIR FUNDS

Amendment to the Written Instrument Establishing and Designating

Shares of the William Blair Emerging Leaders Growth Fund

The undersigned, the Board of Trustees of the William Blair Funds (the “Trust”), a statutory trust organized pursuant to a Declaration of Trust dated September 3, 1999 (the “Declaration of Trust”), pursuant to Section 9.3 of Article IX of the Declaration of Trust, do hereby amend the Written Instrument Establishing and Designating Shares of the William Blair Emerging Leaders Growth Fund dated November 30, 2007, as amended on February 18, 2010 (the “Written Instrument”) as follows:

WHEREAS, the Board of Trustees of the Trust, pursuant to Sections 6.2 and 6.3 of Article VI of the Declaration of Trust, executed the Written Instrument establishing and designating a new series of Interests of the Trust to be known as the “William Blair Emerging Leaders Growth Fund” (the “Series”); and

WHEREAS, a name change for the Series has been recommended and the Board of Trustees has approved the name change for the Series.

RESOLVED, that the Board of Trustees of the Trust hereby re-designates the Series to be known as the “William Blair Emerging Markets Leaders Fund” effective on such date as determined by the President of the Trust.

IN WITNESS WHEREOF, the undersigned have this 23rd day of October, 2012 signed these presents, in one or more counterparts, each of which shall be deemed an original but all of which shall together constitute one and the same document.

/s/ Vann A. Avedisian	/s/ Donald L. Seeley
Vann A. Avedisian	Donald L. Seeley
/s/ Phillip O. Peterson	/s/ Michelle R. Seitz
Phillip O. Peterson	Michelle R. Seitz
/s/ Donald J. Reaves	/s/ Thomas J. Skelly
Donald J. Reaves	Thomas J. Skelly
	/s/ Richard W. Smirl
	Richard W. Smirl